Question

His son has been late three times ________ the morning of last Thursday.

1. A.
   in
2. B.
   on
3. C.
   since
4. D.
   until

Answer 1

C
因为前面是现在完成时态，故后面只能用since，意为“自上星期四上午以来”；如果用on的话，此句就是一般过去时态。