Mr. Smith ________ these days. I think he should take a holiday before he burns out.

A. has been overworking                                B. overworked

C. had overworked                                   D. was overworking

Mr．Smith ________ these days．I think he should take a holiday before he burns out．

1. A.
   has been overworking
2. B.
   overworked
3. C.
   had overworked
4. D.
   was overworking