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Ex9/
1. I could ride a bicycle when I was 7 years old.
2. I wasn't able to visit Glasgow because I didn't have enough time.
3. I think robots are able to do housework in the future.
4. This game show is interesting, but that game show is so boirng.
5. In Viet Nam, April is the hottest month of the year.
6. My father always read the newspaper and watches the TV news in the morning.
7. Unless we use the cars all the time, we will keep the air cleaner.

Ex10/
1. I could play chess when I was six.
2. We couldn't play football because it was raining.
3. Could you speak English when you were five?
4. Could robots clean the house ten years ago?
5. He will go camping next week.