**Core Concept**
The question is testing the student's knowledge of the ovarian cycle and the presence of oogonia, which are the female germ cells in the ovaries. Oogonia are present in the ovaries during fetal development and undergo a process called oogenesis to form oocytes.

**Why the Correct Answer is Right**
Oogonia are present in the ovaries at birth, and their number is maximum at around 6-8 million. This number decreases significantly during fetal development and further decreases during the first few years of life due to the process of oogenesis. The presence of oogonia in the ovaries is a critical aspect of female reproductive biology, and understanding this concept is essential for the diagnosis and management of various reproductive disorders.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because oogonia are not present in the ovaries during puberty. While the ovaries are active during puberty, the number of oogonia has already decreased significantly.
**Option B:** This option is incorrect because the ovaries do not produce oogonia in adults. The process of oogenesis is completed during fetal development, and the number of oogonia is fixed by birth.
**Option C:** This option is incorrect because the ovaries are not producing new oogonia after birth. The number of oogonia in the ovaries is maximum at birth and decreases significantly over time.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the number of oogonia in the ovaries is maximum at birth and decreases significantly over time. This concept is crucial for understanding various reproductive disorders, such as premature ovarian failure and infertility.

**Correct Answer:** D.