## **Core Concept**
The question tests the understanding of fetal ovarian development, specifically the timeline of **oogonia** presence in the ovaries. Oogonia are the female germ cells or early oocytes in the ovaries.

## **Why the Correct Answer is Right**
The correct answer, **20 weeks of gestation**, is the period when the maximum number of oogonia can be seen in the ovaries. During fetal development, around 20 weeks of gestation, the ovaries contain the maximum number of oogonia. After this peak, the number of oogonia starts to decline due to a process called **atresia**, where many of these cells undergo programmed cell death. By birth, the number of oogonia significantly decreases, and the remaining cells enter a dormant stage as **primary oocytes**, arrested in prophase I of meiosis.

## **Why Each Wrong Option is Incorrect**
- **Option A: 10 weeks of gestation**. While oogonia start to develop early in fetal life, 10 weeks is too early for the maximum number to be present.
- **Option B: 30 weeks of gestation**. By 30 weeks, the number of oogonia has already started to decline from its peak.
- **Option D: At birth**. By the time of birth, the number of oogonia has significantly decreased due to atresia, and most of the remaining oocytes are in a dormant state.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **peak number of oogonia** in human ovaries occurs around **20 weeks of gestation**, after which there is a significant decline. This fact is crucial for understanding ovarian development and the limited number of oocytes available for reproduction throughout a female's lifetime.

## **Correct Answer: C. 20 weeks of gestation**