从句缺少宾语时用that,缺少原因状语时用why
如:
The reason that he told us is not true.(在从句中做直接宾语)
The reason why he didn't attend the meeting is not clear.(在从句中做原因状语)
我说的明白吗?
此外,The reason 后的从句也可能是同位语从句,判断标准:只保留The reason 和从句(不看主句其他部分),然后再两者之间加一个is如果语义句法成立,就是同位语从句.换句话说,先行词与同位语从句有逻辑主表关系.
如有问题请追问.