直流回路压降是指蓄电池放电时,()之间的电压之差。A、直流配电屏的输入端至直流配电屏

题型:单项选择题

问题:

直流回路压降是指蓄电池放电时,()之间的电压之差。

A、直流配电屏的输入端至直流配电屏的输出端

B、直流配电屏的输出端至用电设备的输入端

C、蓄电池组的输出端至直流配电屏的输入端

D、蓄电池输出端的电压与直流设备受电端

考点:移动通信代维人员专业考试基站、延伸、综合接入专业共用知识基站、延伸、综合接入专业共用知识题库
题型:单项选择题

设α=(1,1,-1)T是[*]的一个特征值.
(Ⅰ) 确定参数a,b及特征向量所对应的特征值;
(Ⅱ) 问A是否可以对角化说明理由.

题型:单项选择题
已知A={x|f(x)=
x-1
+
2
8-2x
}
,B=(-∞,a),若A∩B=A,求实数a的取值范围.
题型:单项选择题

Recently I bought an ancient Chinese knife,__________was reasonable.

A.which price

B.the price of which

C.its price

D.the price of that

题型:单项选择题

起重电磁铁供电电缆或放电电阻短路时,线圈产生的过电压可达5000V,必须采取适当的预防和保护措施,以确保供电电缆、放电电阻及控制电路工作可靠。

题型:单项选择题

阅读理解。

     Food sometimes gets poisoned with harmful things. A person who eats such food can get an illness called

food poisoning. Food poisoning is usually not serious, but some types are deadly, The symptoms of food

poisoning usually begin within hours of eating the poisoned food. Fever is one of the most common symptoms.

     Certain microorganisms (微生物) cause most types of food poisoning. Bacteria and other microorganisms

can poison eggs, meat, vegetables, and many other foods. After entering the body, these tiny living things

release (释放) poisons that make people sick.

     Some chemicals can also cause food poisoning. They are often added to food while it is being grown,

processed, or prepaid. For example, many farmers spray chemicals on crops to kill weeds and insects. Some

people may have a bad reaction to those chemicals when they eat the crops.

     Some plants and animals contain natural poisons that are harmful to people. These include certain kinds of

seafood, grains, nuts, seeds, beans, and mushrooms.

     When people handle food properly, the risk of food poisoning is very small Microorganisms multiply rapidly

in dirty places and in warm temperatures. This means that people should never touch food with ditty hands or

put food on unwashed surfaces. Food should be kept in a refrigerator to stop microorganisms from gnawing.

Meat needs to be cooked thoroughly to kill any dangerous microorganisms. People should also wash food

covered with chemicals before eating it. Finally, people should not eat raid mushrooms or other foods that grow

in the wild. Some of these foods may contain natural materials that are poisonous to humans. In addition, some

types of fish can be poisonous.

     Most people recover from food poisoning after a few days of resting and drinking extra water. If people eat

natural poisons, they must go to the hospital right away to have their stomachs emptied.

1. Which of the following statements is NOT true?

A. Food when poisoned can make people sick.

B. Food poisoning means death.

C. Food poisoning comes in varieties.

D. Food poisoning can be serious.

2. We know from the passage that the symptoms of food poisoning _____.

A. are always accompanied by a fever

B. are too common to be noted

C. can be noticed within hours

D. can be ignored

3. Food poisoning can be caused by all the following EXCEPT _____.

A. some chemicals

B. low temperatures

C. some tiny living things

D. certain natural materials

4. From Paragraph 5, we can learn that _____.

A. mushrooms should not be eaten

B. vegetables are safer than meat and seafood

C. natural poisons are more dangerous than chemicals

D. different types of food should be handled differently

5. It can be inferred from the passage that _____.

A. natural materials are safe in food processing

B. chemicals are needed in food processing

C. food poisoning can be kept under control

D. food poisoning is out of control

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