.Not all the students sitting in the back row can see the words on the blackboard _________.

Look! Someone is cutting a tree on the moon.–It _______ be true, Granny. Our teacher says there is no air there.

Would you like to watch the 2014 Nanjing Youth Olympic Games this summer holiday?—I’d love to. I believe it ________ be fun.

There a math test tomorrow.

You should really smoking because it’s bad for your health.