英语 关系副词the reason why 与the reason which /that 的区别及用法

the reason why ,why 代替先行词 reason 在定语从句中状语,表原因；the reason which / that , which / that 代替先行词在定语从句中主语、宾语或表语.如：
The reason why he was late is that he couldn't catch the first bus. 他来迟的原因是他没赶上第一班车.（状语）
The reason that / which he explained to his teacher is not reasonable. 他向老师解释的理由一点都不合理. （宾语）
The reason that / which is obviously right is sometimes wrong indeed. 明显正确的理由有时确是错的.（主语）

the reason why 后面加结果
eg ：The reason why he late is his mother 's illness
the reason which /that 后加原因
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