通常RNC的机房高度应满足不小于（）m.

下面说法正确的是（　　）

A．在电场中，电场强度大的点，电势必定高

B．电荷置于电势越高的点，其所具有的电势能也越大

C．电场中电场强度大的地方，沿电场线方向电势降落快

D．一带电粒子只受电场力作用在电场中运动时，电势能一定变化

按照企业所得税的有关规定，下列各项中不得确认为坏账损失的是( )。

A．逾期3年以上仍未收回的应收账款，且对方已确无偿债能力

B．关联方之间的往来账款

C．债务人被依法宣告破产，其剩余财产确实不足清偿的应收账款

D．符合条件的债务重组发生的债务重组损失

凝胶过滤法主要用于蛋白和核酸分离，又称为分子筛层析法，其常用介质是（）。

A.聚丙烯酰胺

B.琼脂糖

C.琼脂糖-聚丙烯酰胺

D.葡聚糖

E.琼脂糖-葡聚糖

不是肾上腺皮质分泌的是（）

A.皮质醇

B.醛固酮

C.性激素

D.肾上腺素

E.盐皮质激素

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.