Some of you may have finished unit one._____; you can go on to unit two

A.If you may

B.If you do

C.If not

D.If so

答案及解析： D

解析：

考查省略。If so ="If" you have done so。句意：你们中的一些人可能已经完成第一单元,如果这样的话,你可以继续第二单元。