Green products are becoming more and more popular because they are environmentally _________.

Mum told me not to drive____ high spead on the busystreet.

When asked to explain he did to make his students so fascinated with his lessons the teacher paused and thought deeply.

Don’t you think there are too many cars on the road—I really think so. If there are ______ people driving, there will be ______ pollution (污染).

e made full preparations, but it remains______whether they will be able to do a good job in the experiment.