填空题。

1. In 1846, the United States____    (向……宣战 ) Mexico.

2. They  _____ (定居 ;习惯于) new towns.

3. ____  (人们相信)that before long the mix of nationalities will be so great that there will be no

    distinct major racial or cultural groups.

4. I ____  (一起合作 ) a couple from my hotel and hired a car.

5. He was puzzled by a math problem and then a new idea suddenly___ (使想起) him.