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21. We have ______ cat, ______ dog, and ______ goldfish as pets.
A. a/an/an B. an/an/the C. the/the/a D. an/a/ the

22. ______ Earth is the third planet from ______ Sun.
A. a/a B. an/the C. the/the D. the/a/the

23. We should take a shower instead ______ bath to save water.
A. in B. of C. on D. for

24. ___________________ means using something again.
A. reduce B. recycle C. reuse D. relearn

25. My father ______________ to the zoo tomorrow.
A. go B. will go C. goes D. went

26. If we cut down more forests, there ___________ more floods.
A. are B. have been C. were D. will be

27. They cancelled their picnic ________ the weather was bad.