it is bad 在句子中是什么成分

解答如下：it为代词，指代an action,在that宾语从句作动名词performing的宾语成分,is为宾语从句系动词，bad为that宾语从句表语成分。具体分析如下：

To know that an action is good(主语）// requires（谓语动词）// knowing that refraining from performing it is bad（宾语：动名词短语作宾语成分）.

参考译文：要知道一个行为是好的，就得知道不去做是不好的。

以上句子结构为A requires doing sth(To know that A is good requires knowing that refraining form doing sth is bad)

以上句子语法结构分析如下

(1)句子主语：T o know that an action is good

(2)谓语动词： requires

(3)宾语: knowing that refraining from performing it is bad

宾语语法结构分析如下

动名词：knowing

动名词后接that宾语从句: that refraining from performing it is bad

宾语从句引导词:that

宾语从句主语: refraining from performing it(动名词短语作主语，it指代an action)

宾语从句系动词:is

宾语从句表语:bad