Teenagers should by all means ________ their studies though there are a lot of attractions around them．

1. A.
   devote to
2. B.
   fix on
3. C.
   concentrate on
4. D.
   keep on

The teachers and parents all agree that teenagers should by all means _______ their studies though there are a lot of attractions around them.

A．devote to         B． fix on         C．concentrate on         D．keep on