13. His ability is beyond question; has been in doubt is he is prepared to work hard A.

问题补充：

13. His ability is beyond question; has been in doubt is he is prepared to work hard

A. what; that

B. which; whether

C. what; whether

D. that; that

答案：

A. what; that

B. which; whether

(答案→)C. what; whether

D. that; that

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