It’s uncertain _______ side effect the medicine will bring about , although about two thousand patients have taken it ．

1. A.
   that
2. B.
   what
3. C.
   how
4. D.
   whether

. It is uncertain __ side effect the medicine will bring about, although about two thousand patients have taken it.

  A. that                B. what             C. how              D. whether

It is uncertain________side effect the medicine will bring about，although about two thousand patients have taken it.

A. that      

B. what 

C. how        

D. whether

It is uncertain____side effect the medicine will bring about，although about two thousand patients have taken it.

A.that??? B.what??? C.how??? D.whether

It is uncertain      side effect the medicine will bring about , though about one thousand patients have taken it.

A. that          B. whether        C. what            D. how