Cathy said she speak four languages.[ ]
A. may
B. could
C. would
D. can
答案：B
—My bike is broken.
—____________. [ ]
A. I don't know
B. You should be careful
C. Let me help you mend it
D. That't all right
提高真空处理时脱氢效果的主要方法是（）。
