鄙人需要几道英语选择题

Is this factory __________ some foreign friends visited last Friday?

A. that B. where C. which D. the one

Is this the factory __________ he worked ten years ago?

A. that B. where C. which D. the one

The wolves hid themselves in the places __________ couldn’t be found.

A. that B. where C. in which D. in that

The freezing point is the temperature __________ water changes into ice.

A. at which B. on that C. in which D. of what