Insert hundred, thousand, million, billion in the singular or plural forms.

1. Over the past two years, over _____ (million) immigrants found work, many illegally.

2. _____ (thousand) of bees have been stolen from a British university.

3. Two _____ (hundred) years after the Constitution was signed, free-enterprise economics had produced doubtful results.

4. State prosecutors investigate more than _____ (thousand) cases of stolen babies in Spain.

5. According to the estimate, the world population has exceeded the number of seven _____ (billion) people.

6. Officials issued public warnings after _____ (hundred) of sharks were spotted in the waters.

7. Roman Abramovich threw a party costing five _____ (million) pounds.

8. _____ (million) of people in West Africa must be protected from a serious food crisis.

9. It has been found that walking ten _____ (thousand) steps a day will help you drop undesired pounds.