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1 The town of Pompeii was destroyed by a volcanic ________.
2 When there's a _______ people die from lack of food.
3 Earthquakes and tsunamis are natural _______.
4 Air ______ is caused by smoke from factories, car exhaust fumes, and aeroplanes.
5 Many scientists believe that global warming is caused by the _____ effect.
6 To help protect the environment, you can _____ your rubbish.
7 If we do not protect rare animal species, they may become ______.