Assertion : Combinations of progesterone and esterogen are used as antifertility drugs.
Reason : These control the pregnancy.

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion**: The assertion states that combinations of progesterone and estrogen are used as antifertility drugs. This is correct because these hormones are commonly used in contraceptive methods.

2. **Understanding the Reason**: The reason given is that these hormones control pregnancy. This is also correct as they play a crucial role in regulating the menstrual cycle and preventing ovulation, which is essential for pregnancy to occur.

3. **Linking Assertion and Reason**: The assertion and reason are related. Antifertility drugs, which contain combinations of progesterone and estrogen, work by controlling the processes involved in pregnancy, such as ovulation and the maintenance of the uterine lining.

4. **Conclusion**: Since both the assertion and reason are correct and the reason explains the assertion, we can conclude that both statements are true, and the reason is the correct explanation for the assertion.

**Final Answer**: Both the assertion and reason are correct, and the reason is the correct explanation of the assertion.

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