9 Join the sentences, as in the example. Put commas where necessary. Write D for defining, ND for non-defining. Decide whether the relative pronoun can be omitted or not.

Решение:

1. Buckingham Palace is in London. It is the residence of the Queen of England. Buckingham Palace, which is in London, is the residence of the Queen of England. (ND – relative pronoun cannot be omitted)
2. I bought a book yesterday. It's very interesting. The book, which I bought yesterday, is very interesting. (D – relative pronoun can be omitted)
3. Sam's birthday is on Saturday. He's having a party this weekend. Sam, who is having a party this weekend, has his birthday on Saturday. (ND – relative pronoun cannot be omitted)
4. I've been studying all day. That's why I'm very tired. I've been studying all day, which is why I'm very tired. (ND – relative pronoun cannot be omitted)
5. The best time to visit Scotland is on New Year's Eve. Hogmanay takes place then. The best time to visit Scotland is on New Year's Eve, when Hogmanay takes place. (ND – relative pronoun cannot be omitted)
6. Amy is taking part in the carnival. She has made her costume herself. Amy, who has made her costume herself, is taking part in the carnival. (ND – relative pronoun cannot be omitted)