英语that从句如果是被动句,动词be可以省略吗?that从句如果是被动句,动词be可以省略吗,在that存在的情况下.例如：it is the book that (was) borrowed yesterday.

1.Do you know the boy (that is )called Tom?
2.Do you know the boy (who is ）sleeping soundly?
3.Do you know the boy (that is )considered to be hard-working?
4.Do you know the boy whose father is a famous scientist?
5.Do you know the boy who is hardworking?
6.Do you know the boy that is famour for his folk songs?
有上述例句来看，不能一概而论，需要具体情况具体分析。
由123句可以得出结论：
若定语从句是由在从句中做主语的关系代词引导、谓语中含有be做助动词、且谓语含有三个以上的单词构成时，可以把关系代词和助动词be一起省略。
然而高中阶段一般不讲这一规律，并且这是不完全归纳得出的东西，并不普遍适用。

it is the book that I borrowed yesterday. 这样是对的，也可以去掉that，是先行词作宾语。你给的句子不正确。

这个应该不是这么说吧，borrowed 应该是过去分词作后置定语吧

不能，你举的这个例子是个强调句。

不可省略
解析如下:
被动语态中各种时态都需要"be"动词的变化来体现如下:
一般现在时：am／is／are＋done
一般过去时：was／were＋done
一般将来时：will／shall be＋done
过去将来时: would be+done
现在进行时：am／is／are being＋done
过去进行时：have／has been＋done
现在完成时：have／has been＋done
过去完成时: had been+done
从上可以看出被动句中的be是不可省的.要省除非你把主语和be动词都省略.
用非谓语形式的过去分词表被动.如
It is the book that was borrowed yesterday.
可转化成
It is the book borrowed yesterday .
其实如果没有上下文语境,提问者所例句子只能是一个强调句构:
即 "It is + 强调部分 + that ."
It is the book that was borrowed yesterday.
如果你把"was"省略掉.那么强调句还原成陈述句如下:
The book borrowed yesterday.
从上面可以看出,此句省略了"was"就相当于你把一个动词的承受者,变成了发出者,既不合逻辑又违背了原句句意.
If you still feel confused ,please leave message!