定语从句用which不用that的情况

以下是定语从句用which而不用that的情况。

1. 非限制性定语从句的情况下肯定不能用that作引导词。非限制性定语从句由逗号隔开，所以在阅读时如果看到逗号后有that的情况，那么这个that肯定不是用于引导定语从句。
Green tea is rich in anti-oxidants, which gets your blood moving and improves your energy level. 绿茶富含抗氧化剂，能促进血液循环并提升能量水平。
They offered him some money, which he refused politely. 他们要给他一些钱，他婉言拒绝了。

2. 限制性定语从句中只能用which而不用that的情况比较少见，但需要注意以下情形。
1) 当定语从句是由“介词 + 关系代词”引导时，其中的关系代词就只能用which而不能用that。
They lost sight of the reasons for which they went to war. 他们忽略了他们去打仗的原因。
Humor was a means by which the American writers would win popular acceptance of their readers. 幽默是美国作家迎合读者的一种手段。

2) 当先行词为 that 或 those 时，关系代词只能用which而不用that，以避免重复。
Natural water is that which contains impurities. 天然水是一种含有杂质的水。
Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。

3) 另外，which 还可以用作限定词，后跟名词，that 则没有这个用法。
I may not be in the office, in which case you could leave me a note. 我不一定在办公室 ，如果是那样你可以给我留个便条。
The Shang dynasty, during which period China's written history began, made its capital in Henan. 商朝定都河南，中国有文字记载的历史是从这个时期开始的。