Question

when you read the book,you'd better make a mark( )you have any questionA,at which

when you read the book,you'd better make a mark( )you have any questionA,at which B the place where C,at where D where 可以选C吗,where引导宾语从句.我知道D是状语从句可以用，但是C当成名词性从句理解可以吗

Answer 1

选A, at which=where
这是一个定语从句，用which 指代any questions，又因为这个Mark是在Question上的，所以要多一个at，在从句中，which的前面也需要保留这个at.
这句话的意思是：当你读这本书的时候，最好在你有疑问的地方做个记号。
去掉从句修饰，该句为：When you read the book,you'd better make a mark at the question.