Do you know the difficulty he had the work?A. on finishingB. to finishC. finishingD. finis

问题补充：

Do you know the difficulty he had the work?

A. on finishing

B. to finish

C. finishing

D. finished

答案：

A. on finishing

B. to finish

(答案→)C. finishing

D. finished

解析：考查非谓语动词。句意：你知道完成这项工作他们有多少困难吗？现在分词作状语表示主语正在进行的伴随性动作，he had为后置定语，修饰difficulty，故选C。