问题
New technology ______ to make sure that the cars, taxis, buses and trains we use ______ the air
A:is used; not to pollute
B:has used; is not polluted
C:is being used; do not pollute
D:has been used; to pollute
B:has used; is not polluted
C:is being used; do not pollute
D:has been used; to pollute
正确答案是：
