He wrote a letter ___C___ he explained what had happened in the accident.
A.what B.which C.where D.how
因为从句中不缺名词成分,所以不是which
而根据句意来看是,应该是
He wrote a letter on which he explained what had happened in the accident.
on which=where什么叫不缺名词成分？你就理解为不缺主语和宾语which是充当主语的？which指的是letter所以是on which =wherein which 是where你记错了方位词+which都等于where,不要局限于一个老师说 将先行词带入从句 然后可以知道从句缺少状语 这怎么看出来的？是怎么带入的？这个其实要看句意，他阐述了在事故中发生的事，在哪？在信上。。所以是缺状语奥！！我懂了，万分感谢！！