5.指人可用that who, 以下情况多用who;
Those people做先行，There be的结构中；
例句：
1) Those who are for the plan, please raise your hands.
赞成计划的人请举手。
2) People who create computer viruses are called hackers.
制造电脑病毒的人被称为黑客。
3) There was once a little boy who came to the net bar to play games every night.
曾经有一个小男孩每天晚上都来网吧玩游戏。
先行指人不定代，从中做主who要在；
先行词是指人的不定代词，如 one 、someone 、anyone 、nobody 等词，或指人的关系代词在定语从句中做主语，要用who, 而不用that。
例句：
1）Nobody who knows a little scientific knowledge will believe you.
懂得一点科学知识的人都不会相信你的话。
解析：nobody是指人的不定代词，用who, 不用that。
2）The thief who pretended to be a manager was caught stealing a car.
那个装扮成经理的贼在偷车时被当场抓获。
解析：who指人，在定语从句中做主语。
两个定从一起来，不要重复你有才；
一个先行词有两个定语从句时，关系代词要避免重复使用。
A plant that can cure diseases, which was known by the ancient Chinese , is called Chinese herbal medicine. 一种能够治病的，被古代中国人所熟知的植物，叫做中药。
6.定从之中少定语，whose为你唱一曲；
Whose指人又指物，所属关系要记住。
Whose也是一个关系代词，在定语从句中做定语，表示人与人、人与物或物与物之间的所属关系，特别要注意，物与物之间的关系也用whose。
例句 1)Is there anyone in your class whose family is in the country?
解析：anyone是先行词，whose=anyone’s，在定语从句中做定语。
例句 2) Pass me the book whose cover is red.
解析：the book是先行词，whose=the book’s, 在定语从句中做定语。
7.As/which在句末，若有否定as错；
as和 which都可指代前面一句话，请看例句:
1）Alice received an invitation from her boss, which came as a surprise.
爱丽丝受到了她老板的邀请，这使她感到吃惊。
2）The weather turned out to be very good, which was more than we could expect.
天气结果变好了，这是我们没有预料到的。
若有否定as错；
3）The result of the experiment was very good, _______ we hadn't expected.
A. when B. that C. which D. what
【简析】答案是C。由于非限定性定语从句是否定结构，只能用which引导，不能用as来替代which。
句首只能用as,还有认知猜想词；
置于句首时，非限定性定语从句只能用as引导。例如：
As is known to everybody, the moon travels round the earth once every month.
众所周知，月亮每月绕地球一周。
与表示认知猜想的词，如know, expect, see, report, 连用时，要用as。
1）As we know, smoking is harmful to one's health.
我们知道，吸烟对健康有害。
2）As is expected, his daughter entered a key university.
正如人们所期望的那样，他的女儿考入了一所重点大学。