Underline the correct item.
1 Greenhouse gases/fuels surround the earth. 2 We're taking a survival research/course this weekend. 3 He is a marine/natural biologist who studies sea creatures. 4 4 Global/Climate warming is threatening natural animal habitats. 5 The best part of the trip was the stunning scenery/scene. 6 They have turned the area into a natural/nature reserve.
Most university students prefer to stay in a youth hostel/hotel. Sea waters/levels are rising due to melting glacier ice.