He once worked in a company he went abroad for further study.A. from whichB. after thatC

问题补充：

He once worked in a company, he went abroad for further study.

A. from which

B. after that

C. after which

D. from this

答案：

A. from which

B. after that

(答案→)C. after which

D. from this

解析：句意在公司工作以后，与once worked呼应。