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问题 单项选择题

关于现场直埋电缆说法错误的有（）。

A.走向应按施工总平面布置图的规定，沿主道路或固定建筑物等的边缘直线埋设

B.埋深不得小于0.7m

C.电缆紧邻四周均匀敷设不小于50mm厚的细砂，然后覆盖砖或混凝土板等硬质保护层

D.转弯处和大于等于40m直线段处，在地面上设明显的标志

答案

参考答案：D

单项选择题

Many animals recognize their food because they see it. So do humans. When you see an apple or a piece of chocolate you know that these are things you can eat. You can also use other senses when you choose your food. You may like it because it smells good or because it tastes good. You may dislike some types of food because they do not look, smell or taste very nice. Different animals use different senses to find and choose their food. A few animals depend on only one of their senses, while most animals use more than one sense.

Although there are many different types of food, some animals spend their lives eating only one type. The giant panda(大熊猫) eats only one particular type of bamboo(竹子). Other animals eat only one type of food even when given the choice. A kind of white butterfly(蝴蝶)will stay on the leaves of a cabbage, even though there are plenty of other vegetables in the garden. However, most animals have a more varied diet(多样化饮食). The bear eats fruits and fish. The fox eats small animals, birds and fruits. The diet of these animals will be different depending on the season.

Humans have a very varied diet. We often eat food because we like it and not because it is good for us. In countries such as France and Britain, people eat food with too much sugar. This makes them overweight, which is bad for their health. Eating too much red meat and animal products, such as butter, can also be bad for the health. Choosing the right food, therefore, has become an area of study in modern life.

Certain animals change their choice of food when （）.

A．the season changes

B．the food color changes

C．they move to different places

D．they are attracted by different smells
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单项选择题

复合按钮的常开触头与常闭触头具有（）联锁。

A.常开

B.常闭

C.电气

D.机械
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