as和which在引导非限制性定语从句时除位置外有什么区别

有一点需要注意的是“介词+关系代词”引导时,关系代词不能用as
eg：I finished my homewordk ahead of time,after which I sat some time watching TV我提前做完了作业,随后我坐下来看了会儿电视.after后只能which修饰I finished my homework.而不能跟as
做选择题时,还是按照语法规则去做
eg：1.（ ）is known to everybody ,the moon travels round the earth once every month.月亮每月围绕地球转一周,这是人人皆知的.由于在句首,本题选 as
2.she heard a terrible noise,（ ） brought her heart into her mouth.她听到可怕地声音,这让她把心都提到嗓子眼了.由于在句尾,填写which