should have done sth的sth比be supposed to do sth的sth更贴近现实,是客观正确该做的事
be supposed to do sth的事情只是理论上应该做的事,有可能是依照常理该做的,依照他人的命令该做的,是在某人主观观念中正确的事.
还有不解请追问有时态的区分么？should have done涵盖所有时态,有时态的话也是上下文体现了be supposed to do可以通过be的变化来体现时态