应该用who
1 在限制性定语从句中，当先行词指人时，关系词可用who(m)或that，二者常可互换。
但在下列情况中，用who(m)，而不用that：
(1) 当先行词是one， ones， any， few， anyone， anybody， someone， somebody， everyone
everybody等词时。如：
Is there anyone who can answer this question?
He was among the few who managed to live through the enemy prison camp.
注：在非正式文体中可以说：You’re the one that knows where to go.)
(2) 当先行词是he， they， those， people， person等词时。如：
He who wants to catch fish just not mind getting wet.
Those who are against the proposal put up your hands.
注：在固定结构的谚语或习语中，可用he that…。如：
He that promises too much means nothing.
(3) 当先行词有较长的后置定语修饰时。如：
Do you know the writer in blue with thick glasses who is speaking at the meeting?
(4) 在分隔式定语从句中，若先行词指人，为了明确修饰关系，应当用who(m)。如：
A new master will came tomorrow who will teach you German.
There’s only one student in the school who/whom I wanted to see.
I was the only person in my office who was invited.
(5) 两个定语从句同时修饰一个指人的先行词，第二个定语从句常用who(m)来引导，如：
She is the only girl I know who can play the guitar.
2在限制性定语从句中，当先行词指物时，关系词可用which或that，二者常可以互换；但在下列情况中，只能用that，不用which：
(1) 当先行词是all， a lot， (a) little， few， much， none， anything， something， everything， nothing等词时。如：
All that can be done has been done.
In this factory I saw little / much that was different from ours.
(2) 当先行词被all， any no， much， little， few， every等限定词所修饰时。如：
We heard clearly every word that he said.
(3) 当先行词是序数词或被序数词所修饰时。如：
The first thing that should be done is to get the tickets.
When people talk about Hangzhou， the first that comes to mind is the West Lake.
(4) 当先行词是形容词最高级或被形容词最高级所修饰，以及先行词被序数词和形容
词最高级同时修饰时，如：
Is that the best that you can do?
That’s the most expensive hotel that we’ve ever stayed in.
This novel is the second best one that I have ever read.
(5) 当先行词被 the very， the only， the next， the last等所修饰时。如：
This is the very book that I want to find.
(6) 当先行词为指人和指物的两个并列名词词组时。如：
The guests spoke highly of the children and their performances that they saw at the Children’s Palace.
She described in her compositions the people and places that impressed her most.
(7) 当主句是以which开头的特殊疑问句时。如：
Which is the car that killed the boy
somebody作先行词关系代词用什么
关系代词可以用whom
