[A]: The pollen sterility has been attributed to the malfunctioning of tapetum.
[R]: Premature degeneration of the tapetum deprives the developing spores of its nutri- tion.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that pollen sterility is linked to the malfunctioning of the tapetum. The tapetum is the innermost layer of the anther, which plays a crucial role in the development of pollen grains.

2. **Identifying the Role of Tapetum**: The tapetum is responsible for providing nutrition to the developing spores (microspores) during their development into pollen grains. It is a multinucleated layer that surrounds the sporogenous tissue.

3. **Analyzing the Reason**: The reason provided states that premature degeneration of the tapetum deprives the developing spores of nutrition. This means that if the tapetum degenerates too early, it will not be able to supply the necessary nutrients to the spores, leading to their failure to develop properly.

4. **Connecting Assertion and Reason**: Since the assertion (pollen sterility due to malfunctioning of tapetum) is true, and the reason (premature degeneration of tapetum leading to lack of nutrition for spores) correctly explains why the assertion is true, both the assertion and reason are valid.

5. **Conclusion**: Therefore, both the assertion and the reason are true, and the reason provides a correct explanation for the assertion.

### Final Answer:
Both the assertion and the reason are true, and the reason is the correct explanation for the assertion.

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