完型填空。

    We know health is very important 1 us. So we must keep2. How to do it? We should do more exercises and eat healthy food. We can play sports. For example, we can play football and basketball. We can run. We can attend the high jump and long jump. If you don't  like 3sports. You can go for 4walk every day. It's very good .We should eat fruit, vegetables and other healthy food. We should eat less sweet food and fried food. Breakfast5important. We must eat breakfast every day.

式子$\sqrt{x-1}$在实数范围内有意义，则x的取值范围是（  ）