要说下为什么,()the book,he found out some answers to this question .A.as he reading B.at his reading C.as reading D.on reading
问题描述：
要说下为什么,()the book,he found out some answers to this question .A.as he reading B.at his reading C.as reading D.on reading
答
选D,此处意为“一~就”,on/upon为介词,后接名词或动词的ing形式.
On/upon reading reading the book,he found out some answers to this question.
若用as,as用作连词,连接一个时间状语从句,意为“当~时候”.应该为 As he was reading the book,he found out some answers to this question.故C不对.
at没有这样的用法.