▶️ Answer/Explanation
Menstruation is the phase of the menstrual cycle where the uterine lining (endometrium) breaks down and is shed, resulting in a decrease in thickness. Looking at the graph, the thickness starts to decrease from Day $1$ and reaches its lowest point around Day $4$ to Day $5$. After this point, the lining begins to repair and thicken again under the influence of estrogen. Since the decline stops and the “trough” of the graph ends around Day $4$, this represents the conclusion of the shedding phase. Therefore, Day $4$ is the most accurate choice for the last day of menstruation.
✅ Answer: (A)
✅ Answer: (A)
▶️ Answer/Explanation
In a typical $28$-day menstrual cycle, Luteinizing Hormone (LH) reaches its peak concentration just before the midpoint of the cycle. This “LH surge” triggers ovulation, which is the release of a mature egg from the ovary, typically occurring on day $14$.
The other options are incorrect because: * FSH (Follicle Stimulating Hormone) acts during the follicular phase (days $1$-$14$) to mature the egg, not up to day $21$. * Oestrogen primarily repairs the lining in the first half of the cycle, while Progesterone (produced by the corpus luteum) is responsible for maintaining the lining from day $14$ to $28$. * The repair and thickening between days $4$ and $14$ is stimulated by Oestrogen, not Progesterone.
✅ Answer: (B)
▶️ Answer/Explanation
Testosterone is the primary androgen produced by the testes in males. During puberty, its levels increase significantly, triggering the development of secondary sexual characteristics such as a deeper voice, facial and body hair growth, and increased muscle mass. While adrenaline regulates the “fight or flight” response and insulin manages blood glucose, oestrogen is the primary hormone for female sexual development. Therefore, testosterone is the hormone specifically responsible for masculine physical traits.
✅ Answer: (D)
✅ Answer: (D)