Use relative adverb to combine each pair of sentences below

Ex8. Use relative adverb to combine each pair of sentences below
1. This is the house. We often stay in this house in summer.
=> ___
2. I’ll show you the second hand bookshop. You can find valuable books in this shop.
=> ___
3. I have not decided the day. I’ll go to London on that day.
=> ___
4. He was born on the day. His father was away on that day.
=> ___
5. The book is a telephone directory. We can look up telephone numbers in this book.
=> ___