问题补充：
When you have difficulty in learning new words, you can the dictionary.
A. look up
B. turn up
C. turn to
D. turn over.
答案：
A. look up
B. turn up
(答案→)C. turn to
D. turn over.
解析：turn to the dictionary相当于refer to the dictionary.查字典look up a word in a dictionary.
