( )1. I study English ______ making flashcards.
A. of B. by C. in D. on
( )2. It’s very difficult to learn English well, but you can’t _____.
A. put it up B. take it up C. look it up D. give it up
( )3. They enjoyed _____ piano.
A. play B. playing C. playing the D. to play a
( )4. I don’t know _____ it next.
A. what to can do B. how to do C. what can I do D. how can I do