Помогите сделать упражнение!

Complete these sentences by filling in 'who', 'which', 'that', 'where' of 'whose'.
1. Clowns ....... are really funny are hard to find.
2. The mountains ...... we have a cabin are covered by three metres of show.
3. The ring l gave her, ..... cost a lot of money, was eaten by our dog last hight.
4. Robert,...... house has been in the market for one year, wants to travel to India.
5. Nina and her husband,...... celebrated there 25th anniversary last mounth, will be at the party.