是因为主语被only修饰
限制性定语从句只能用that的几种情况
1、当先行词是anything,everything,nothing (something 除外),few,all,none,little,some等代词时,或者是由every,any,all,some,no,little,few,much,each等修饰时
(1) Have you taken down everything (that) Mr.Li has said?
(2) There seems to be nothing (that) seems impossible for him in the world.
(3) All that can be done has been done.
(4) There is little (that) I can do for you.
注意1：部分时候that可以省略,如部分例句将that用括号括住.
注意2：当先行词指人时,偶尔也可以用who
(4) Any man that/.who has a sense of duty won’t do such a thing.
2、当先行词被序数词修饰
The first place that they visited in London was the Big Ben.
3、当先行词被形容词最高级修饰时
This is the best film that I have seen.
4、当形容词被the very,the only,the same,the last ,any,little等修饰时
(1) This is the very good dictionary that I want to buy,
(2) After the fire in his house,the old car is the only thing that he owned.
当先行词指人时,偶尔也可以用who
(3) Wang Hua is the only person in our school who will attend the meeting?
5、当先行词前面有who,which等疑问代词时
(1) Who is the man that is standing there?(2) Which is the T-shirt that fits me most?6、当先行词既有人,也有动物或者物体时
Can you remember the scientist and his theory that we have learned?
7.当关系代词在定语从句中做表语
The village is no longer the one that it used to be 10 years ago.
8.当在there be句型中,通常情况下用that,不用which