Isn’t it time you got down to ________ the papers?

A. mark
B. be marked
C. being marked
D. marking

答案D
考查非谓语动词的用法。get down to doing sth.是固定搭配,“开始做某事”;to为介词,后面接动名词或名词,所以排除A、B项。you和mark之间为主动关系,所以D项正确。
温馨提示:答案为网友推荐,仅供参考