The light will be thrown ______ the cause of cancer by research that is now in progress

1. A.
   to
2. B.
   upon
3. C.
   in
4. D.
   for

 The light will be thrown ______ the cause of cancer by research that is now in progress.

       A. to        B. upon       C. in               D. for

The light will be thrown ______ the cause of cancer by research that is now in progress.

       A. to        B. upon       C. in               D. for

The light will be thrown ______ the cause of cancer by research that is now in progress.

      A. to                             B. upon                         C. in                       D. for

The light will be thrown ______ the cause of cancer by research that is now in progress．

A．to        B．upon           C．in        D．for