问题补充:
The scientists are beating their brains trying to a solution to the problem.
A. come about
B. come across
C. come out
D. come up with
答案:
A. come about
B. come across
C. come out
(答案→)D. come up with
解析:考查词组:A. come about发生B. come across遇到C. come out出版D. come up with提出,想出,句意:科学家正绞尽脑汁找出问题的解决办法。选D。