They began to think about what use could be ______ such materials.

Entering the orchard, you will find apple trees are ______ fruit, fragrance drifting around. 

—Sorry, I have to               now. It’s time for class.—OK. I’II call back later.

As time ______, my mother gets older and older.

I've visited a lot of different places and stayed in lots of different hotels, but none of them____________ this one.