Their plan was ______. With it we had little trouble in finishing the work.
A.successB.succeedC.a successD.a successful在线课程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。