1. _____ as much as one-fifth of the trees have been cut down.
A. said B. It said
C. It is said that D. As is said
2. _____ some mammals came to live in the sea is not known.
A. Which B. Since C. Although D. How
3. Could you tell me________?
A. when did Tom come back B. when does Tom come back
C. when Tom will come back D. when Tom comes back
