分清界线
distinguish boundaries clearly
分清敌我
distinguish clearly between friend and foe
分清是非
distinguish clearly between right and wrong
分清好坏
distinguish clearly between good and bad
分清主次
distinguish between primary and secondary
分清职责
have a clear idea of one's job responsibilities
分清两类矛盾
distinguish between two types of contradiction
分不清两种不同的概念
cannot distinguish between two different concepts
一片汪洋，分不清哪是天哪是水。
Looking at this vast ocean, it is difficult to tell where the water ends and the sky begins.