（50分）关于定语定语从句的一些小问题

1 可以，例如：This is a house,in which we once lived.非限制性定于从句的一个特点时去掉定于从句后不影响原句意思，也可以说只要不影响原意，都可以用非限制性定于从句（多说一点，如将上面那句话说成This is the house in which we once lived，此时用the就是定于从句，不能用非限制性定于从据，即定于从据不能省略）

2 可以，成为表语从句，用where引导，表示地方。其他表语从句例子：
The problem is when we can get a pay rise.
He has become what he wanted to be ten years ago.
(另外你的原句是不是该说成This house is the one we were once invited to.)

3 是的，as只能引导整个句子，且一般放在句首，如：
As we know, smoking is harmful to one's health.
当然也可以是强调内容的不同而将位置改变，如强掉吸烟有害而不是人人皆知，可说成Smoking is harmful to one's health，as we know.

1、应明确非限定性定语从句恐怕只有as和which可代整个主句，而这两个词能用介词+关系代词替换吗？我还找不到这样的例子。
This is a house,in which we once lived.
which代指house，而不是整个主句。
如果是说介词+关系代词可否引导非限定性定语从句，答案是肯定的，而且“介词+关系代词”前可有some, any, none, both, all, neither, most, each, few等代词或者数词
He loved his parents deeply, both of whom are very kind to him.
2、可以。zlw3565584说的对。
3、as引导的定语从句能代替前面的单个词，as是个难点。as引导限制性定语从句主要结构有