【巩固练习】
1. Don’t talk about such things of __________ you are not sure.
A. which B. what
C. as D. those
2.Is this the factory __________ you visited the other day?
A. that B. where
C. in which D. the one
3.Is this factory __________ some foreign friends visited last Friday?
A. that B. where
C. which D. the one
