## **Core Concept**
Puberty is a complex physiological process involving the activation of the hypothalamic-pituitary-gonadal (HPG) axis, leading to the development of secondary sexual characteristics and reproductive maturity. This process is primarily driven by changes in hormone levels, notably the increase in gonadotropin-releasing hormone (GnRH) secretion. The onset of puberty is marked by specific physical changes.

## **Why the Correct Answer is Right**
The correct answer involves understanding the physiological changes occurring at puberty. One key event is the growth spurt, which is largely driven by the increase in growth hormone and the sex steroids (estrogen and testosterone). Another critical aspect is the development of secondary sexual characteristics.

## **Why Each Wrong Option is Incorrect**
- **Option A:** [Insert option A text here] - This option is incorrect because [provide a brief explanation for why option A is wrong, focusing on the physiological or clinical inaccuracies].
- **Option B:** [Insert option B text here] - This option is incorrect because [provide a brief explanation for why option B is wrong, focusing on the physiological or clinical inaccuracies].
- **Option C:** [Insert option C text here] - Although this option might seem plausible, it is incorrect because [provide a brief explanation for why option C is wrong].

## **Clinical Pearl / High-Yield Fact**
A memorable point for exams is that the first sign of puberty in girls is typically breast development (thelarche), followed by the growth spurt, and then pubic hair development (pubarche). In boys, the first sign is often testicular enlargement, followed by the growth spurt and then pubic hair development.

## **Correct Answer:** D. True