Shirley _____ a book about environmental protection, but I wonder whether she has finished it.

A. wrote                                            B. had written

C. has written                                    D. has been writing

Shirley ________ a book about environmental protection, but I wonder whether she has finished it．

1. A.
   wrote
2. B.
   had written
3. C.
   has written
4. D.
   has been writing