Correct Answer: B) Adolescence

Explanation: Adolescence is the period between childhood and adulthood when physical, mental, and emotional changes occur in the body, leading to reproductive maturity. It usually starts around 11 years and continues till about 18–19 years.

Correct Answer: C) 10–12 years

Explanation: In most girls, puberty starts a little earlier than boys, commonly around 10–12 years, when changes such as breast development and onset of menstruation begin. These are average values; exact age can vary from person to person.

Correct Answer: C) Wearing school uniform

Explanation: Increase in height, change in voice, and development of secondary sexual characters are biological changes occurring during adolescence. Wearing a school uniform is a social or cultural practice and not a biological change of adolescence.

Correct Answer: B) The stage when the body becomes capable of reproduction

Explanation: Puberty refers to the time during adolescence when reproductive organs become functionally mature and the body is capable of reproduction. It is marked by a series of physical and hormonal changes.

Correct Answer: B) Teenagers

Explanation: Adolescents are generally in the age group of 13–19 years. Since these ages end with the word “teen” (thirteen, fourteen, etc.), they are commonly called teenagers.

Correct Answer: C) 11–19 years

Explanation: Adolescence usually begins around 11 years and continues till about 18–19 years, though actual age may vary slightly from person to person. This is the period of rapid growth and development.

Correct Answer: B) Adolescence

Explanation: Adolescence marks the transition period from childhood to adulthood. Physical, emotional, and social changes occur during this stage, preparing an individual for adult life.

Correct Answer: B) Rapid increase in height

Explanation: During puberty, adolescents experience a sudden and rapid increase in height due to faster growth of bones and muscles. This growth spurt is a characteristic change of this stage.

Correct Answer: B) Broader and more muscular

Explanation: Due to the action of testosterone and increased muscle growth, boys develop broader and more muscular shoulders, which is a secondary sexual character in males.

Correct Answer: B) Widening of hips and development of breasts

Explanation: During puberty, girls typically show widening of hips and development of mammary glands (breasts) as a result of the action of the hormone oestrogen. These are important secondary sexual characters in females.

Correct Answer: B) Growth spurt

Explanation: The term “growth spurt” is used for the sudden and rapid increase in height and weight during adolescence. After this period, the rate of growth slows down and eventually stops when adult height is reached.

Correct Answer: C) Genetic factors and nutrition

Explanation: The final height of an individual is largely determined by heredity (genes inherited from parents). However, good nutrition and healthy lifestyle during growing years help a child reach his or her maximum potential height.

Correct Answer: B) Growth spurt – rapid increase in height

Explanation: Growth spurt refers to the rapid increase in height during adolescence. Other options are either unrelated or incorrect in the context of this chapter.

Correct Answer: A) New layers of bone are added at the ends

Explanation: Long bones grow in length by the addition of new bony tissue at the ends (growth plates). This makes the arms and legs longer during adolescence, contributing to increase in height.

Correct Answer: B) Endocrine glands

Explanation: Hormones are chemical messengers produced by endocrine glands. These glands are ductless, so hormones are released directly into the blood and transported to target organs.

Correct Answer: C) Pituitary gland

Explanation: The pituitary gland is called the master gland because it secretes hormones that control the functioning of many other endocrine glands, such as thyroid, adrenal, testes, and ovaries.

Correct Answer: D) Testosterone

Explanation: Testosterone is the male sex hormone produced by testes. It brings about changes like facial hair, deeper voice, and increased muscle mass in boys during puberty.

Correct Answer: B) Oestrogen

Explanation: Oestrogen is produced by the ovaries in females. It is responsible for changes such as development of breasts and widening of hips, which are secondary sexual characters in girls.

Correct Answer: A) Regulate blood sugar level

Explanation: Insulin is a hormone secreted by the pancreas. It helps maintain normal blood sugar (glucose) levels. Deficiency of insulin causes diabetes, in which blood sugar level becomes high.

Correct Answer: C) Thyroid gland

Explanation: The thyroid gland, located in the neck region, secretes thyroxine. This hormone regulates the body’s metabolism and is important for normal growth and development.

Correct Answer: A) Stress hormone

Explanation: Adrenaline is secreted by adrenal glands during stress, fear, or emergency situations. It prepares the body to face the situation by increasing heart rate, breathing, and blood supply to muscles, hence often called the “fight or flight” or stress hormone.

Correct Answer: B) Pituitary gland

Explanation: The pituitary gland secretes growth hormone, which controls the growth of the body. Too much of it can cause abnormal increase in height, while too little can result in stunted growth.

Correct Answer: B) They secrete hormones directly into the blood

Explanation: Endocrine glands lack ducts. Therefore, their secretions (hormones) are released directly into the bloodstream, which carries them to specific target organs where they act.

Correct Answer: C) Salivary gland

Explanation: Salivary gland is an exocrine gland that secretes saliva through ducts into the mouth. Thyroid, adrenal, and pituitary are endocrine glands as they release hormones into the blood without ducts.

Correct Answer: B) Pituitary gland

Explanation: The pituitary gland secretes hormones that stimulate the testes to produce testosterone and sperm. Thus, the pituitary plays a central role in controlling reproductive functions in males.

Correct Answer: A) Hormones from pituitary gland

Explanation: Pituitary hormones act on ovaries to initiate the production of female sex hormones (oestrogen and progesterone) and maturation of ova. This starts around puberty in girls.

Correct Answer: C) Female sex hormones

Explanation: Menstrual cycle is regulated by female sex hormones produced by the ovaries under the control of the pituitary gland. These hormones prepare the uterus for pregnancy each month and, in the absence of fertilisation, lead to menstruation.

Correct Answer: C) Testes – male sex hormones

Explanation: Testes in males produce the male sex hormone testosterone and sperm. Ovaries in females produce female sex hormones (oestrogen and progesterone) and ova. Pancreas secretes insulin, which is not a sex hormone.

Correct Answer: B) Ovary

Explanation: Ovaries store immature ova (eggs) and release one mature ovum roughly every month during the reproductive age of a female. The uterus is where a fertilised egg develops, whereas vagina is the birth canal.

Correct Answer: B) Is shed off during menstruation

Explanation: Every month, the uterus develops a thick lining with blood vessels to receive a fertilised egg. If fertilisation does not occur, this lining breaks down and is released through the vagina as menstrual flow.

Correct Answer: B) Menarche

Explanation: Menarche is the term used for the first menstrual bleeding in a girl, marking the onset of reproductive maturity. Menopause is the stage when menstruation stops permanently in older women.

Correct Answer: B) Secondary sexual characters

Explanation: Secondary sexual characters appear at puberty and help differentiate males and females externally, such as facial hair in boys and development of breasts in girls. They are not directly involved in the act of reproduction.

Correct Answer: C) Growth of beard and moustache

Explanation: Growth of facial hair is a secondary sexual character specific to males. Ovaries and uterus are parts of the female reproductive system, and widening of hips is a secondary sexual character of females.

Correct Answer: B) Development of breasts

Explanation: Development of breasts is a prominent secondary sexual character in females, influenced by the hormone oestrogen. Other options listed are either male characters or incorrect.

Correct Answer: C) Fertilisation

Explanation: The sex of the baby is decided at the moment when the sperm fuses with the ovum (fertilisation). The type of sex chromosome carried by the sperm (X or Y) determines whether the child will be a boy or a girl.

Correct Answer: B) XY

Explanation: In humans, males have one X and one Y sex chromosome (XY), whereas females have two X chromosomes (XX). This difference plays a key role in determining the sex of the offspring.

Correct Answer: B) Father only

Explanation: The mother’s egg always carries an X chromosome. The father’s sperm may carry either an X or a Y chromosome. If an X-bearing sperm fertilises the egg, the baby will be XX (girl). If a Y-bearing sperm fertilises, the baby will be XY (boy). Hence, the father determines the sex of the baby.

Correct Answer: B) Boy (XY)

Explanation: The ovum always has X. If sperm carries Y, then the combination becomes XY, which develops into a male child. For a girl, the combination must be XX (sperm carrying X fertilising an X-bearing ovum).

Correct Answer: C) All nutrients in proper amount

Explanation: A balanced diet contains carbohydrates, proteins, fats, vitamins, minerals, water, and roughage in correct proportion. Adolescents need a balanced diet for proper growth, strong bones, healthy muscles, and good immunity.

Correct Answer: B) Foods rich in protein

Explanation: Proteins are body-building nutrients. They help in the growth and repair of body tissues and are very important during adolescence when muscles and bones are rapidly growing.

Correct Answer: B) Keep the body clean and dry

Explanation: During adolescence, sweat and oil gland activity increases, which can lead to body odour and pimples. Maintaining personal hygiene by regular bathing, washing hair and clothes helps prevent skin infections and keeps the body fresh.

Correct Answer: B) Taking balanced diet and exercising

Explanation: Eating a balanced diet, regular physical exercise, enough sleep, and avoiding harmful substances are healthy practices. Skipping meals or using addictive substances is harmful for health and should be avoided.

Correct Answer: B) Sudden mood swings

Explanation: Hormonal changes during adolescence can cause emotional ups and downs. Adolescents may feel happy at one moment and sad or irritated at another. Understanding these changes and talking to trusted adults can help them cope better.

Correct Answer: B) Taking addictive drugs

Explanation: Addictive substances (like tobacco, alcohol, or drugs) are extremely harmful to health and can damage the brain, liver, lungs, and heart. Healthy coping methods include communication, exercise, and constructive hobbies.

Correct Answer: C) Complete physical, mental, and social well-being related to reproduction

Explanation: Reproductive health includes physical health of the reproductive organs, mental health (correct attitude), and social well-being (responsible behaviour). It is not only about producing children or absence of disease.

Correct Answer: C) Using tobacco and alcohol

Explanation: Tobacco, alcohol, and other drugs are addictive and harmful. They can seriously damage organs like lungs, liver, heart, and brain. Adolescents should firmly say “no” to such substances to protect their health and future.

Correct Answer: B) Thyroxine

Explanation: Metamorphosis in frogs (tadpole changing into adult frog) is controlled by thyroxine, the hormone produced by the thyroid gland. Proper amount of iodine in water and food is necessary to produce thyroxine.

Correct Answer: B) Insect hormones

Explanation: In insects like silkworm, the transformation from larva to pupa to adult (metamorphosis) is controlled by specific insect hormones. This shows that hormones control life cycle changes in many organisms, not just humans.

Correct Answer: B) Goitre

Explanation: Iodine is required by the thyroid gland to make thyroxine. If diet does not contain enough iodine, thyroid gland enlarges, resulting in a neck swelling called goitre. Iodised salt helps prevent this deficiency.

Correct Answer: B) Well-informed and trusted sources like parents, teachers, and doctors

Explanation: Adolescents often have doubts about bodily and emotional changes. They should always seek correct and scientific information from reliable and trusted adults or qualified health professionals, instead of depending on rumours or misleading sources.