We can never expect____ bluer sky unless we create _____ less polluted world.

Why don’t you turn to Professor Lee for some advice— _____. What if he refuses to help or something

We are glad to hear that the terrorists ________ by the brave policemen several days ago.

How about your journey to Shanghai — Everything was wonderful except that our car ________.

There are many beautiful hats here. I really don’t know_______.