什么叫母线不完全差动电流保护?

题型:问答题

问题:

什么叫母线不完全差动电流保护?

考点:电气值班员考试电气值班员技师考试电气值班员技师考试题库
题型:问答题
阅读理解。
    All living things on the earth need other living things to live. Nothing lives alone. Most animals must
live in a group, and even a plant grows close together with others of the same kind. Sometimes one
living thing kills another, one eats and the other is eaten. Each kind of life eats another kind of life in
order to live, and together they form a food chain (链条). Some food chains are simple, while others
are not. But all food chains begin with the sun, and all food chains become broken up if one of the links
disappears.
    All life needs sunlight to live on. But only plants can use sunlight directly. Plants are "factories". They
make food from sunlight, water and things in the soil and air. Plants feed all other living things. Animals
can only use the sun's energy after it has been changed into food by plants. Some animals feed directly
on plants, others eat smaller animals. Meat-eating animals are only eating plants indirectly. 
    What about human beings? We are members of many food chains. We eat rice, vegetables, and fruits
and so on. We also eat meat and drink milk. But men often break up the food chains. They kill wild
animals. They also make rivers, lakes and seas polluted, when these rivers, lakes and seas are polluted,
the fish in them can not be eaten. If men eat the fish, they will get strange diseases.
    Each form of life is linked to all others. Breaking the links puts all life in danger.
1. How does every living thing on the earth live? 
[ ]
A. Each plant can live alone.
B. Each animal can live alone.
C. If living things want to live, they must kill each other.
D. Every living thing on the earth can't live without others.
2. Which living things can use the sun's energy directly?
[ ]
A. Animals.
B. Plants.
C. Animals and plants.
D. All living things.
3. Who often break up the food chains?
[ ]
A. Human beings.
B. Animals.
C. Plants and animals.
D. Men and wild animals.
4. Which of the following do you think is the best title for this passage?
[ ]
A. The sun's energy.
B. Plants.
C. Food Chains.
D. Living Things.
题型:问答题

在图中画出入射光束AO透过玻璃砖,再进入空气中传播的大致光路图。

题型:问答题

心脏向心性肥大的本质是()

A.心肌细胞数目增加

B.肌节的并联性增生

C.肌节的串联性增生

D.心肌纤维长度加大

E.以上都不是

题型:问答题

磁力泵在使用过程中遇到哪几种现象时需要紧急停车?

题型:问答题

企业内部组织没有独立法律地位,不能以自己的名义对外从事生产经营活动,因而,企业内部组织不能成为经济法律关系的主体。 ( )

更多题库