It was the second-hand car that the mechanic spent the whole afternoon in the factory.A.

问题补充：

It was the second-hand car that the mechanic spent the whole afternoon in the factory.

A. in repair

B. repaired

C. repairing

D. to repair

答案：

A. in repair

B. repaired

(答案→)C. repairing

D. to repair

解析：考查非谓语动词。It is … that …为强调句型，repairing the second-hand car为动名词做主语，故选C。