Look! A man is cutting a tree on the moon.—-It ______ be true. The teacher said there is no air on the moon.

The electric lamp ____ by Edison.

－It won’t take long to clear up after the party if we all volunteer to help.－That’s right. _____________.

are in trouble, Mike is always willing to_______ a hand

When you lose your way in the city, you can _________the policemen _________help.