Though this question is very difficult，if you ________ trying you will find the right answer.
A.keep up
B.keep on
C.keep out
D.keep off
网友回答
B解析这题考查词组辨析： keep on“继续，反复做”，符合题意。keep up“保持，跟上”；keep out“使留在外面，扣留”；keep off“使不接近，避开某话题”。句意：尽管这个问题很难，但是如果你继续不断地尝试，你会得到正确