Reading without thinking is like eating without digesting, Never accept whatever is written in a book, for even experts __________ make mistakes．

1. A.
   must
2. B.
   should
3. C.
   will
4. D.
   can

Reading without thinking is like eating without digesting,Never accept whatever is written in a book,for even experts     make mistakes.

A.must   B.should   C.will   D.can