Unless you work as hard as you can, you won’t ______ your classmates.A.fall behindB.keep on withC.keep up withD.catch up
参考答案：
C解析本题考查动词短语辨义。句意: 如果你不尽可能的努力学习，你就跟不上你的同学。fall behind 落后；keep on不和with搭配；keep up with跟上……，不落后于；catch up跟上……；后接with后才可接宾语。
