Question

1. February, which is the second month of the year, is the month ---- many of my colleagues take vacation for skiing.
a. when
b. in which

2. The dress ---- the movie star is wearing weighs about fifty pounds.
a. that
b. which

3. Flying squirrels ---- live in tropical rain forests spend most of their time on the trees.
a. that
b. which

Answer 1

1.In which
2.that
3. Which

Hope it helps :)

Answer 2

Answers
1) in which
2) That
3) which