The scientists are beating their brains trying to a solution to the problem.A. come about

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。