试题题干
I had no clue what he was trying to suggest because he just couldn't （） the subject.
参考答案
正确答案：
试题解析
本题考查动词短语辨析。keep to：坚持，遵守，固守（习惯等）；keep up with：赶得上，和…保持联系；keep off：让开，不接近，避开某一话题；keep out of：躲开，置身…之外。根据后面的subject可以判断，四个选项中A选项最符合题意。句意：我不知道他想暗示什么，因为不能围绕一个主题来讲。