After _______ seemed half an hour, the teacher gave us the correct answer.

After _______ seemed half an hour, the teacher gave us the correct answer.

1. A.
   what
2. B.
   that
3. C.
   which
4. D.
   it

 After _______ seemed half an hour, the teacher gave us the correct answer.

A. what      B. that      C. which       D. it 

After _______ seemed half an hour, the teacher gave us the correct answer.

A. what　　 B. that　　 C. which　　　 D. it

After _______ seemed half an hour, the teacher gave us the correct answer.