1. Carol said the work would be done by October, _____personally I doubt very much.

A. it   B. that  C. when   D. which

2.       _______ is mentioned above, the number of the students in senior high school is increasing. 

A. Which   B. As   C. That   D. It

3. The fence in our garden, ______ my father built many years ago, has lasted for a long time. 

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

4. There’s still much ______ can be improved about it.

A. which   B. that   C. if    D. what

5. When lost in work, ____ he often was, he would forget all about eating and sleeping. 

A. what    B so   C. just like   D. as