阅读理解。

     American schools begin in September after a long summer vacation (假期). There are two terms in a

school year: the first term is from September to January, and the second is from February to June. Most

American children go to public schools (公立学校). High school students take only four or five subjects

at a time. They usually go to the same classes every day, and they have an assignment for every class.

After class they have many activities. After high school, many students go to college.

1. Most American children start school life in _______.

A. September  

B. February  

C. June  

D. January

2. How many vacations do American children have each year?

A. One.    

B. Two.        

C. Three.  

D. Four.

3. Students in the high school have _______ subjects at a time.

A. four    

B. five    

C. six    

D. four or five

4. Which of the following is false (错误)?

A. In July students don't need to go to school because of vacation.

B. Students have the same classes every day.

C. Students don't have homework for every class.

D. Most American children go to public schools.

5. After class students _______.

A. do homework  

B. go back home  

C. have many activities  

D. go to movies

(2011年绍兴一中检测)我国最新一代核聚变装置“EAST”在安徽合肥首次放电、显示了EAST装置具有良好的整体性能，使等离子体约束时间达1000 s，温度超过1亿度，标志着我国磁约束核聚变研究进入国际先进水平．合肥也成为世界上第一个建成此类全超导非圆截面核聚变实验装置并能实际运行的地方．核聚变的主要原料是氘，在海水中含量极其丰富．已知氘核的质量为m₁，中子的质量为m₂，He的质量为m₃，质子的质量为m₄，则下列说法中正确的是(　　)

A．两个氘核聚变成一个He所产生的另一个粒子是质子

B．两个氘核聚变成一个He所产生的另一个粒子是中子

C．两个氘核聚变成一个He所释放的核能为(2m₁－m₃－m₄)c²

D．与受控核聚变比较，现行的核反应堆产生的废物具有放射性