北师大高中英语模块1Unit2：One of the reasons people are interested in exploring space is that they wonder if there is life on any other planets. (P22)

解释：the reason that后接具体原因，如：The reason that he was ill yesterday is such a bad excuse.意为：那个他昨天生病的理由真是个糟糕的借口。(也可认为是同位语从句）

 the reason why后接对这个理由的修饰, 或者是现在需要解释的一个状况。如：The reason why he was late is that he was ill.在这里，he was late 是一个需要解释的情况, 所以用the reason why，这里用到一个句型：the reason why ... is that...

另：先行词reason后接定语从句，如定语从句中缺少原因状语，则用why引导，若缺少主语或宾语，则用that或which引导，如：

This is the reason why he got angry. (缺状语)

He told us a reason that / which sounded reasonable.

(作定语从句的主语)

Can you remember the reason he told us last week?

(作told的间接宾语，可省去that)