662　the reason why…is that

◎ 这个句型表示“做……的原因是……”，why 引导的从句看作同位语从句，对reason作具体解释，that引导表语从句，that不可省。这个句型可简化为：The reason is that…，但不可说The reason is because…。

The reason why he didn't come to the party is that his son fell ill. 他没有来参加聚会的原因是他儿子病了。

The reason why he can't stay is that he has something urgent to do. 他不能留下来的原因是他有些急迫的事情要做。

The reason is that she thought she was unfit for it. 理由是她认为她不是很能胜任。