Конечно, я помогу тебе соединить предложения, используя относительные местоимения и наречия. Вот расширенные ответы на каждый из вопросов:
John is my cousin. He is a magician.
- John, who is my cousin, is a magician.
- John, who is a magician, is my cousin.
York is a city. It is in the north of England.
- York is a city which is in the north of England.
- York, which is in the north of England, is a city.
Mark Jacobs is the author. His book became a best seller.
- Mark Jacobs, whose book became a best seller, is the author.
- Mark Jacobs is the author whose book became a best seller.
Dennis is going to Paris. He will visit the Eiffel Tower there.
- Dennis, who is going to Paris, will visit the Eiffel Tower there.
- Dennis is going to Paris, where he will visit the Eiffel Tower.
This is the piano. He bought it at an auction.
- This is the piano that he bought at an auction.
- This is the piano which he bought at an auction.
В этих предложениях относительные местоимения и наречия (who, which, that, whose, where) помогают связать два предложения в одно, делая текст более плавным и связным.