1. (2022八下·重庆期中) 根据知文内容，从 A、B、C、D 四个选项中选出一个能填入相应空格内的最佳答案。

Studies show that CPR (心肺复苏术) can save people's lives in dangerous1. And experts say people need to know the2of CPR and learn it.

The3it is done, the more likely (可能的) it is for people to be saved. The American Heart Association4 more schools to teach students about CPR.

When 15-year-old Seth Johnson learned CPR at school, he learned it5. Two weeks later, Seth used CPR to save  his dad Mark with his elder sister Claire6Mark had a heart attack (心脏病发作).

That day, their father Mark suddenly felt7. Then, things got worse. Claire ran in and let her dad8. Seth called 911 right away and then started doing CPR. Seth put his hands on the center of his dad's chest (胸部) and started to press hard and fast. He pushed on his chest 30 times, and then he gave his dad rescue breaths (人工呼吸).

Claire once 9 CPR at school, too. After about four minutes of CPR, Seth was saved. Then Claire kept on doing it. About two minutes later, doctors arrived. 10 Seth and Claire, their dad Mark spent only five days in hospital and finally got better.