Choose the correct item.

1. He is a ... biologist who studies sea creatures.

2. ... warming is threatening natural animal habitats.

3. The best part of the trip was the stunning ... .

4. Greenhouse ... surround the earth.

5. We're taking a survival ... this weekend.

6. They have turned the area into a ... reserve.

7. Most university students prefer to stay in a youth ... .

8. Sea ... are rising due to melting glacier ice.