2. There are about 750 million English speakers in the world, and this number (increase) ____is increasing______ fast.

3. Factories (not dump) __won't dump________ waste into rivers if the government fines them heavily.

4. The kangaroo (become) _____has become_____ a symbol of Australia since 1973.

5. If there were more trees in this area, the air (be) _____wouldn't be _____ fresher.

6. The earthquake occurred at midday when they (have) ___were having _______ lunch.