Explanation: Adolescence is the transitional phase between childhood and adulthood when a person undergoes physical, emotional and psychological changes. It usually begins with puberty and includes rapid growth and development of secondary sexual characteristics.

Explanation: Puberty is the biological process that triggers adolescence. It brings hormonal changes leading to reproductive maturity and the development of secondary sexual characteristics.

Explanation: The World Health Organization defines adolescence roughly as 10–19 years. This is when most physical and sexual maturation occurs, though exact ages can vary.

Explanation: Adolescence involves growth in height and bodily changes; permanent loss of height is not a feature. Choices A, B and D correctly describe adolescent changes.

Explanation: Changes during adolescence — hormonal, physiological and psychological — are studied under human biology and physiology because they relate to the functioning of the human body.

Explanation: Adolescence helps individuals reach sexual maturity and form an adult identity, including social roles and emotional independence. Options B and C are features of early childhood; D is incorrect.

Explanation: Secondary sexual characters are traits such as facial hair in males, breast development in females, voice change, and growth of body hair that develop during puberty, helping to distinguish sexes.

Explanation: During puberty, the male voice box (larynx) grows larger, making the voice deeper. Growth of breast tissue and menstruation are female-related changes.

Explanation: Breast development is a prominent female secondary sexual characteristic that occurs during puberty due to hormonal changes, preparing the body for possible future lactation.

Explanation: Testosterone, produced mainly by the testes, promotes development of male secondary sexual characters such as facial hair, deep voice, and increased muscle mass.

Explanation: Estrogen, produced by ovaries, is responsible for breast development, widening of hips and other female secondary sexual changes during puberty.

Explanation: Testosterone stimulates growth of facial hair in boys during puberty. It acts on hair follicles, causing hair transformation and growth patterns typical of males.

Explanation: Both boys and girls experience a growth spurt during puberty. Other listed changes are specific to one sex: deeper voice and sperm production in boys, menstruation in girls.

Explanation: Growth of the larynx during puberty changes the voice pitch. In boys the larynx enlarges more, causing the voice to deepen noticeably.

Explanation: Enlargement of gonads (testes/ovaries) is a primary sexual characteristic because these are directly involved in reproduction. Secondary sexual characters are external and not directly part of reproductive organs.

Explanation: Primary sexual characters are directly involved in reproduction, e.g. testes producing sperm, ovaries releasing eggs. Other options are secondary characters.

Explanation: Testes (testicles) are the male reproductive organs that produce sperm and hormones like testosterone.

Explanation: The ovaries produce eggs (ova) and hormones such as estrogen and progesterone, which regulate female reproductive cycles.

Explanation: Ovulation is when a mature egg is released from the ovary, typically around the middle of the menstrual cycle, making fertilization possible.

Explanation: Fertilization generally occurs in the fallopian tube where the sperm meets the egg shortly after ovulation, before the embryo travels to the uterus for implantation.

Explanation: Seminiferous tubules inside the testes are the site of sperm production (spermatogenesis). After production, sperm mature in the epididymis.

Explanation: The uterus (womb) provides a protective environment where the fertilized egg implants into the lining and the embryo/fetus develops during pregnancy.

Explanation: The vas deferens (ductus deferens) carries sperm from the epididymis towards the urethra, where they mix with seminal fluids and are ejaculated.

Explanation: Menstruation is the discharge of blood and tissue when a fertilized egg does not implant. It's part of the menstrual cycle that prepares the uterus for possible pregnancy.

Explanation: Fertilization is the union of sperm and egg, producing a zygote — the first cell of a new individual which will divide and develop into an embryo.

Explanation: Males produce sperm continuously after puberty into most of their adult life. Option A is false (eggs are not produced after menopause), C is false (both sexes have pituitary glands), D is false (not all mammals menstruate).

Explanation: The pituitary gland (often called the 'master gland') secretes growth hormone and other hormones that regulate development and control other endocrine glands during adolescence.

Explanation: The pituitary gland releases follicle stimulating hormone (FSH) and luteinizing hormone (LH) which stimulate ovaries and testes to produce sex hormones and gametes.

Explanation: The adrenal glands on top of kidneys produce adrenaline that helps the body respond to stress by increasing heart rate and energy release.

Explanation: Estrogen and progesterone, produced by ovaries, regulate the menstrual cycle by preparing and maintaining the uterine lining for possible pregnancy.

Explanation: A surge in luteinizing hormone (LH) from the pituitary triggers the release of a mature egg from the ovary — ovulation.

Explanation: The endocrine system uses hormones released into the bloodstream to send chemical signals to distant organs, regulating growth, metabolism and reproduction.

Explanation: Hormones are chemical messengers secreted by endocrine glands that travel in the blood to target organs and produce specific responses.

Explanation: Hormonal imbalances can alter growth rates, timing of puberty, and development of secondary sexual characters, affecting overall adolescent development.

Explanation: Good hygiene — bathing, proper menstrual hygiene for girls, clean clothes — reduces infections, body odour and supports mental well-being during sensitive adolescent years.

Explanation: Using clean sanitary pads or cloth, changing them regularly, and maintaining cleanliness reduces infections and promotes comfort during menstruation.

Explanation: Nutrients like proteins, vitamins and minerals are essential during adolescence to support growth spurt, bone development and hormonal changes.

Explanation: Exercise, healthy sleep, supportive relationships, and talking about feelings help adolescents manage stress and emotional changes.

Explanation: Acne or pimples are common due to increased oil (sebum) production under hormonal influence during puberty. Proper skincare can help manage acne.

Explanation: Drugs, alcohol or tobacco can harm the developing adolescent brain, causing learning and behavioural problems, addiction and health issues.

Explanation: Sleep is crucial for physical growth, brain development and emotional regulation during adolescence. Poor sleep affects learning and mood.

Explanation: Some vaccines are recommended during adolescence (depending on local guidelines) like HPV vaccine for girls/boys and booster shots to maintain immunity.

Explanation: Hormonal fluctuations and social pressures commonly cause mood swings, heightened emotions and sensitivity during adolescence. These are normal but should be managed supportively.

Explanation: Peers can have positive effects (support, motivation) or negative effects (pressure to take risks). Guidance helps adolescents choose positive influences.

Explanation: Supportive parenting involves listening, offering guidance, and respecting adolescents' growing need for independence, helping them make responsible choices.

Explanation: Media, peers and cultural norms influence how adolescents perceive their bodies. Encouraging healthy habits and realistic expectations helps improve body image.

Explanation: Persistent changes in mood, isolation, loss of interest or severe behaviour changes could signal depression or other issues and should be discussed with a trusted adult or counsellor.

Explanation: Respecting privacy signals trust and supports adolescents' need to develop autonomy in a safe environment — it generally reduces covert risky behaviour.

Explanation: Skills such as decision-making, communication and problem-solving help adolescents navigate choices and resist negative peer pressure.

Explanation: Adults like parents, teachers or counsellors can offer perspective, solutions and protection. Asking for help is a responsible action when problems exceed an adolescent's ability to cope.