Their plan was ______. With it we had little trouble in finishing the work.

A.success

B.succeed

C.a success

D.a successful

答案及解析： C

解析：

抽象名词具体化本题中的a success指成功的事相当于a successful plan。句意：这个计划很成功，有了这个计划我们毫不费劲的完成了工作。