[A]: Man's most characteristic feature in which it differs from all its primate relatives is his large brain and high intelligence.
[R]: A lumbar curve is absent in man which is present in apes

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 man's most characteristic feature that differentiates him from all primate relatives is his large brain and high intelligence. This is true because humans have a significantly larger brain-to-body ratio and advanced cognitive abilities compared to other primates.

2. **Evaluating the Reason**: The reason given is that a lumbar curve is absent in man but present in apes. This statement is incorrect. In fact, humans possess a lumbar curve in their spine, which is an adaptation for bipedal locomotion. Apes, on the other hand, do not have this lumbar curve in the same way that humans do.

3. **Determining the Truth Values**:
- The assertion is true: Humans have a larger brain and higher intelligence compared to other primates.
- The reason is false: Humans have a lumbar curve, while apes do not have it in the same form.

4. **Conclusion**: Since the assertion is true and the reason is false, the correct option is that the assertion is true and the reason is false.

### Final Answer:
The correct answer is that the assertion is true and the reason is false.

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