回答如下：

引导定语从句的关系代词有which，that，who，whom，whose，as 。

1. which指代事物、动物、婴儿，在定语从句中作主语、宾语。作宾语时，which可以省略(非限制性定语从句或介词提前时除外)。它引导非限制性定语从句时，可以指代整个句子。例如：

This is the house (which ) Lu Xun once lived in / in which Lu Xun once lived.

The baby which is crying is my daughter.

I am not interested in the job ( which) you are doing now.

He is ill, which is true.

2. that 指代人、物，在定语从句中作主语、宾语。that作宾语时可省略，但作介词宾语时，介词不能提前。that不能引导非限制性定语从句。例如：

The bridge that was built 50 years ago has been pulled down.

She is the doctor (that ) I mentioned yesterday.

The factory (that) he works in is very large.

3. who、whom指代人，who可以作主语、宾语; 而whom只能作宾语。作宾语时，二者均可省略，但介词提前时，只能用关系代词whom作宾语。例如：

The man who is standing there is my uncle.

The girl who / whom you want to know about / about whom you want to know.

4. whose 指代人、物，在定语从句中作定语。例如：

The girl whose father is a doctor is our monitor.

The book whose cover is red is mine.

We met with a boy, under whose guidance we soon found the girl's home.

5. as(像，正如) 指代人、物，在定语从句中作主语、宾语、表语,常用在such ...as, the same (... ) as短语中或非限制性定语从句中。它引导的非限制性定语从句可以置于句首、句中和句尾，可以指代整个句子。例如：

I don't believe such a person as you (are).

This is the same overcoat as you bought yesterday.

As (正如)we can see, he is a thief.

= He, as we can see, is a thief.

= He is a thief, as we can see.