为什么要用 that 能不能不用that

为什么要用 that 能不能不用that

此处是用that引导的定语从句，只有当引导词that做定语从句的宾语成分时可以省略，其他情况不能省略。此句中that是做从句的主语 所以不可省略。
看下面例子：
The man [(that) I saw in the street yesterday] is my teacher.
The man [that said hello to me yesterday] is my teacher.
The village [(that) I often visit] is my hometown.
The village [that becomes a modern city] is my hometown.
注：带（）的that可以省略，[ ]括着的是定语从句。

宾语从句中间的that可以省略，

Ukip英国独立党
that Ukip 是那个英国独立党 is the only party 是唯一的一个政党。（主句）
that cares about the british countryside（定语从句。修饰party）
要用that作为连接词，这个政党唯一一个关心英国农村的政党。