____ people decorate their room reflects their personlity and lifestyle.A.The way which B.The way C.The way in that D.whatWhy

the way 后的定语从句有三种习惯用法：
in which / that / 不填
1.the way sb do sth
2.the way that sb do sth
3.the way in which sb do sth
至于具体的解释：
the way 表示做某事的方式
例如：people decorate their room in the way
在做句子成分（例句中是主语）时，the way 做先行词，which可以做关系代词替代the way，但一定不能省略介词in， 因此不选A，相应的说法为the way in which people decorate their room
这样说不够简洁，较常用的说法是the way (that) people decorate their room ，其中that可以省略。
不知道你有没有明白，希望能帮到你。

其实a也是对的（比较文学）
只是b用的是zero relative(比较随意 常用在spoken english)
zero relative的用法是 当which/that等等的relative pronoun代的是object(宾语)
就可以去掉which/that等等的relative pronoun...
举个例子吧.
The man who Vicky saw at the concert is Sarah's boss.(比较文学）
也可以写成
The man Vicky saw at the concert is Sarah's boss.(比较随意）