that is one of the reasons that还是why

that is one of the reasons that还是why
如：that is one of the reasons why i told a lie.
还是 that is one of the reasons (that) i told a lie.
其中that 可否省略,记得that在定语从句中做宾语是可以省略,忘记了
什么时候省略（此处的省略又怎么翻译英文呢?leave out?omit?）

都可以用,但都不能省略.
第一个句子：that is one of the reasons why i told a lie.是定语从句.why在从句中做状语,不能省.
第二名句子：that is one of the reasons that i told a lie.是同位语从句.不能省略.
什么时候可以省略?
当先行词是reason,后接定语从句,而定语从句引导词充当从句宾语时就可省略.（这往往是在考试中才会有的句子）如：
The reason (which/that) you gave me is unbelievable.你给我的原因是不可信的.
再问： 翻译成英文 when can I leave out ''that'' in a sentence? 还是 when can I omit ''that'' in a sentence?
再答： 应该不是when, In what conditions can we leave out/omit that in a sentence? 什么情况下我们可以省去句子中的that?