According to a recent U.S. survey, children spent up to 25 hours a week ____ TV.
4. It used to ______ that humans and animals were different and had little in common.
5. The day breaks, _______ the birds are singing.
6. _________, I attended the meeting instead of him last week.
7. When you read the book, you’d better make a mark ______ you have questions.
8. I didn’t see your sister at the cinema. If she ______, she would have met my brother.