As for 可置于句首单独引导状语从句,如:As for the question of life,he feels confused.至于生命的问题,他则非常困惑.这时的"as for" 不能被"about"替换. "about"不能单独引导从句,必须加"how","why","what","where","when"等等才能引导从句,而且是名词性从句居多. 如:He feels sorry about what he has done.他为他所做的事情感到抱歉. "about"后不能去掉"what",不然句子成分残缺,有语法错误.