—Which of these two English books will you borrow?—I’ll borrow ____________ of them because they are very interesting.

They often change the kind of crop in each field ____ few years, for example, growing corn or wheat and then the next year peas or soybeans.

The threats to the health of astronauts in space are very different from ______ on earth. 

—Have you got used to the Chinese food, Robert?—Yes, but I don't like ____ when a Chinese host keeps serving me the food I don't like.

There were a lot of people in the park. We had ______ to take a rest, so we got very tired.