I last saw her a week ago

Question 20. I last saw her a week ago.

A. I have seen her a week ago.

B. I haven't seen her for a week.

C. I haven't seen her since a week.

D. I didn't see her for a week.

Question 21. It took him three hours to finish his homework yesterday

A. He spent three hours finishing his homework yesterday. B. It took him three hours to finish his homework yesterday.

C. He spent three hours to finish his homework yesterday.

D. He spent three hours finish his homework yesterday.