In mammals, the onset of pregnancy causes

Options

A. Secretion of testorsterone
B. Degeneration of ovary
C. Inhibition of further ovulation
D. Inhibition of fertilization.

Answer

**Step-by-Step Solution:**

1. **Understanding Pregnancy Onset in Mammals:**
- When pregnancy begins in mammals, there are significant hormonal changes that occur in the female body. The primary hormones involved are progesterone and estrogen.

2. **Analyzing the Options:**
- **Option A: Secretion of Testosterone**
- Testosterone is primarily a male hormone. While females do produce testosterone, it is not the primary hormone involved in maintaining pregnancy. Therefore, this option is incorrect.

- **Option B: Degeneration of Ovaries**
- The ovaries are responsible for producing eggs and hormones. They do not degenerate during pregnancy; instead, they continue to function to support the pregnancy. Thus, this option is also incorrect.

- **Option C: Inhibition of Further Ovulation**
- During pregnancy, the body inhibits further ovulation to prevent the release of additional eggs. This is a protective mechanism to ensure that the developing embryo has the necessary resources and environment to grow. This option is correct.

- **Option D: Inhibition of Fertilization**
- While fertilization is less likely to occur during pregnancy due to the absence of ovulation, it is not entirely inhibited. If another egg were to be released (which is unlikely), fertilization could still occur. Therefore, this option is incorrect.

3. **Conclusion:**
- Based on the analysis of the options, the correct answer is **Option C: Inhibition of Further Ovulation**. This is the primary physiological change that occurs in mammals at the onset of pregnancy.