在α粒子散射实验中，当α粒子穿过金箔时，下列理解正确的是 [ ] A．与金原子核

某自行车商店实行还本方式销售自行车。自行车现在的单价为500元，已销售 400辆，三年后还本80%，该自行车同类货物市场价为300元，则该商店的计税销售额是 ( )万元。(以上价格均为不含税价格)

A．12

B．16

C．20

D．4

中国的发展离不开世界，世界的繁荣也离不开中国。[ ]

“凤阳地多不打粮，碾子一住就逃荒。只见凤阳女出嫁，不见新娘进凤阳。”“说凤阳，道凤阳，改革鼓点先敲响，三年跨了三大步，如今飞出金凤凰。”导致凤阳花鼓词中安徽凤阳这一变化的原因是当地

A．进行了土地改革

B．开展了“大跃进”和人民公社化运动

C．进行了农业的社会主义改造

D．推行了家庭联产承包责任制

为什么我国必须坚持以公有制为主多种经济成份共同发展的方针？

Have you had a headache during a test Have you ever been so worried about something that you have a headache or even can’t sleep at night If so, then you know what stress is. Stress is what you feel when you are worried about something. This worry in your mind can make your body feel bad. You may feel angry, sad, scared, or afraid—all of which can give you a stomachache or a headache.
However, there are different kinds of stress. Some kinds of stress are good and others are bad. Good stress might happen when you’re called to answer questions in class or when you have to give a speech. This kind of stress can help you to get things better done. For example, you may do a better job on your test if the stress pushes you to prepare better before the test.
On the other hand, bad stress can happen if stress lasts too long. You may not feel well if your parents are fighting, if a family member is sick, if you’re having problems at school, or if anything else makes you unhappy every day. That kind of stress isn’t going to help you. And it can actually make you sick.
The best way to fight stress is to have a balanced life. Make sure you keep your SELF in mind: Sleep, Exercise, Leisure(休闲), and Food. If you get enough sleep and eat properly, and if you exercise and leave time for fun, you’ll probably feel less stressed.