Решение:
Заполняем пропуски подходящими относительными местоимениями:
- 1 That's the man who lives next door.
- 2 Anna, whose father is our Art teacher, is my best friend.
- 3 Sochi is the place where we want to go this summer.
- 4 Sydney Opera House, which is a UNESCO World Heritage Site.
- 5 Anton, whose brother works at the zoo, we met him in Moscow.
Ответ: 1. who, 2. whose, 3. where, 4. which, 5. whose.