The correct answer is: C. She requested her brother not to be late for we would be waiting for him.
The speaker is using the pronoun “we” to refer to herself and someone else. This suggests that she is not alone in waiting for her brother. The use of the word “request” also suggests that she is asking her brother politely not to be late.
The other options are incorrect because they do not accurately reflect the meaning of the sentence. Option A suggests that the speaker is telling her brother not to be late because they would have been waiting for him. However, the sentence does not indicate that the speaker would have been waiting for her brother if he had been late. Option B suggests that the speaker is ordering her brother not to be late because they would be waiting for him. However, the sentence does not indicate that the speaker is in a position of authority over her brother. Option D suggests that the speaker is telling her brother that he should not be late because she would be waiting for him. However, the sentence does not indicate that the speaker is the only person who would be waiting for her brother.