a)
1 which
2 which
3 who
4 where
5 who
6 which
7 where

b)
1 That's the dog which always barks at night.
2 Th a t’s the shop where I bought my wedding dress.
3 Th a t’s the actor who was in Glee.
4 They’re the children who live next door to me.
5 This is the restaurant where they make great pizza.
6 Th a t’s the switch which controls the air conditioning.
7 He’s the teacher who teaches my sister.
8 That's the room where we have our meetings.
9 This is the light which is broken.