美国的主体部分位于（ ）

请认真阅读下面短文，并根据各题所给首字母的提示，写出一个合适的英语单词完整、正确的形式，使短文通顺。
    One night Mr. Lee was driving his wife home from work. She was a nurse in a hospital. It was almost midnight and she was quite tired. She soon fell  a____, Mr. Lee looked at her and smiled.
    Mr. Lee was a  careful and experienced driver. He knew it was safer to drive slowly on a dark night.  A____ a while, he noticed a car following him. It was travelling very fast. Suddenly it overtook(超过) his car.  .
    The driver of the car was in such a  h ____that he did not see the approaching(临近的）truck. To avoid hitting it, he suddenly turned his car. The car skidded(滑) off the road and hit a big tree. The driver and the passengers were injured(受伤). They were badly hurt by the  b____  glass of the car. Mr. Lee quickly  s____ his car and called the police. His wife got out of the car to help them. About twenty-five minutes   l ____ , a police car and an ambulance(救护车)  a____. The injured were taken to hospital.
    The policemen wrote down details of the accident. Mr. Lee and the truck driver told t____ what they could remember. The policemen  

t ____ them for their help. Then Mr. Lee and Mrs. Lee got into their car and continued their journey.

①安闲、闲适的样子。____

②是有点相信，又有点怀疑。表示对真假是非不能肯定。____

③行动、举止过分神气的样子。____

④事物周密完善，找不出什么毛病。____

⑤均匀而又结实。____

图为小芳在“探究口腔中的化学消化”实验的装置。

（1）在进行“探究口腔中的化学消化”实验时，向1号试管滴加2ml水，应向2号试管滴加2ml ____ 。
（2）实验中1号试管的作用是____ 。
（3）小芳实验中滴加碘酒后，两支试管都变成了蓝色。你能分析原因吗？____