New technology ______ to make sure that the cars, taxis, buses and trains we use ______ the air.

1. A.
   is used; not to pollute
2. B.
   has used; is not polluted
3. C.
   is being used; do not pollute
4. D.
   has been used; to pollute

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

. 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

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 mot polluted

C. is being used ; do not pollute　 D. has been used ; to pollute

New technology ____ to make sure that the cars, taxis, buses and trains we use _____ the air.

A．is used; not pollute                                      B．has used; is not polluted

C．is being used; do not pollute                         D．has been used; to pollute