—It's difficult to get to the other side of the river.—I think a bridge ________ over the river.
Which is _____, the sun or the moon?
Lily and Lucy are twins, they _____ good girls, they often help others.
Your book is easier than _____.
Somebody says that a friend _____ a mirror, and I think so.
There is _____ with my bike. I can't ride it.