28. Listen! Who ……………….?

A. is going to sing           B. sings                  C. sing                   D. is singing

29. Nga …………… to the museum yesterday.

A. goes                            B. go                      C. went                  D. going

30. If we burn the rubbish, we will ……………the air.

A. polluting                     B. pollute               C. is pollute           D. polluted
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