621. We can't go out because of the rain．
622. We should make good use of our time．
623. We should save unnecessary expenses.
624. You may have heard of Birth Control.
625. After a pause he continued his story.
626. As you know, I am a very kind person.
627. He dare not tell us his evil conduct.
628. I can express myself in good English.
629. I'll furnish my house with furniture.
630. It seemed as if there was no way out.
631. It's the hottest day I've had so far.
632. Mr. Smith is in charge of this class.
633. Mr. Smith taught English at a school.
634. None of us is afraid of difficulties.
635. Our school is in the east of Beijing.
636. She really wishes her clock had rung.
637. She teaches foreign students Chinese.
638. The question will be settled tonight.
639. The weight is too much for my height.
640. There are mice in Mrs. Lee's kitchen!