Is this factory you visited the other day?A\that B\where C\the one D\in which

Is this factory you visited the other day?A\that B\where C\the one D\in which
Is this factory you visited the other day?A\that B\where C\the one D\in which

Is this factory you visited the other day?A\that B\where C\the one D\in which
C
Is this factory the one you visited the other day?
这个句子的主语是this factory,谓语中的系动词是is,后面you visited the other day是一个定语从句,很明显,这个句子的主句部分缺少表语,定语从句缺少它所修饰的先行词,这就要求空格处填一个名词或代词.B项是副词,D项是一个介词短语,因此排除B、D.
再看A项：that只起引导定语从句的作用.这个定语从句中的谓语visited是一个及物动词,必须带宾语,这个宾语就是that.选A等于是没选,因为that引导定语从句且在从句中充当宾语时可以省略.
C项的the one就是主句的表语,定语从句的先行词.the one后面省略了关系代词that.
不明白的请再问,我在线为你解答.

C\the one （the one 作表语，后面省了that，you visited是定语从句，修饰先行词the one)
原句的主语是this factory
is the one 是系表结构作谓语。

在factory后面的you isited是定语从句，修饰f先行词actory，而且前面的句子缺失表语，因此用介词加which