指事物时，在下列情况下，人们通常用that,而不用which。
1.当先行词为不定代词时:当先行词是指物的a1, lttle, few, much, any; anything, everything, nothing, none, the one时，或先行词被all, lttle, few, much, any, every, no等修饰时，通常用that。如:
All [Everything] that can be done must be done.凡能做的事都必须做。
There was ltte that the enemy could do but surrender.敌人无法，只有投降了。
2.当涉及序数词或最高级时:当先行词是序数词或最高级形容词时，或者先行词被序数词(包括ast,next)、最高级形容词及theonly,thevery等修饰时，通常用that。如:
This is the best dictionary that I've ever used.这是我用过的最好的词典。
The first thing that you should do is to work out a plan.你应该做的第一件事 是订个计划。
3.当涉及the very, the only, the same时:当先行词有the very, the only, the same等修饰时，通常用that。如:
This is the only example that I know.我知道的例子只有这一一个。
Thosearetheverywordsthatheused.那是他的原话。
3.当先行词包括人和物时:此时通常用that。如:
They talked about the persons and things that most impressed them.他们谈论了使他们印象最深的人和事。
