问题补充:
As we all know, Jack is experienced the problem of this kind.
A. to work out
B. at working
C. at working out
D. for working out
答案:
A. to work out
B. at working
(答案→)C. at working out
D. for working out
解析:考查短语be experienced at在某方面有经验。At是介词后面接名词或者动名词。句意:众所周知,杰克在解决这方面的的难题上有经验。Work out解决,算出,故选A。