It is surprising that Jack who is only 39 years old in the field of engineering for 20

问题补充：

It is surprising that Jack, who is only 39 years old, in the field of engineering for 20 years when he entered the company last month.

A. worked

B. had worked

C. has worked

D. working

答案：

A. worked

(答案→)B. had worked

C. has worked

D. working

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