When you read the book
When you read the book ,you had better make a markWhen you read the book ,you had better make a mark _________ you have any question . A.at which B.at where C.where (为什么不选A.B?)
反正是固定用法 mark后面就要接where 如同case situation后面也只能接where
问:If you have any question 要不要加“S”
答:不要,习惯性说法详情>>