The young man was lying on thegrass with his horse _____a tree

More bison were killed．The bison population is thought______ from 60 million to just a few hundred between 1850 and 1910.

In English class, we are often told to ________ dialogues in pairs.

I don’t know when he will arrive.—Don’t worry. I’ll call you as soon as he _____.

For many seniors in some universities, the final year can be an unpleasant experience, _________ that ends campus romance.