Wind power is a source of energy we may return in the near future.
It was a time_______ the killer whales helped the whalers catch the baleen whales.
The most important thing about cotton in history is ______part that it played in _______Industrial Revolution.
–Good morning. I’ve got an appointment with Miss Smith in the Personnel Department. –Ah, good morning. You _____ be Mrs. Peters.
We _____ on this project for four hours. Let’s have a rest.
Would it be ______ for you to pick me up at four o’clock and take me to the airport?