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【简答题】
It was so dark outside the car window that it was hard to see anything. “ Can I have a carrot, Mom?” Bruce asked. “I don’t have any carrots,” his mom said. “How about an apple?” “No,” said Bruce. “It has to be a carrot.” “Why do you want a carrot?” asked his mom “You always say carrots help your eyes.” said Bruce. “If I eat one now, it might help me see in the dark.” Would eating a carrot really help Bruce? What is special about carrots? What makes a carrot special is its color. Carrots are orange because they contain(包含) bta-carotene( 胡萝卜素). Beta-carotene is a way of saying vitamin A. Your eyes need vitamin A. It helps them work. When light hits your eye, very small parts inside turn the light into messages. The messages go to your brain(大脑), and then you know what you’re looking at. Your eye can only turn light into messages when it has a special chemical(化学物质). Your eyes use vitamin A to make the special chemical. Every time your eye changes light into messages, a little bit of the chemical is used up. By the end of the day, you’ve looked at hundreds of things. That uses up a lot of the chemical. Your eyes need to make more. What should you eat if you don’t like carrots? Don’t worry. Other fruits and vegetables have vitamin A, too. The secret is in their color. Most orange or red fruits and vegetables contain beta-carotene, or vitamin A, Sweet vegetable, red peppers(胡椒), Mangoes(芒果) are a few foods that have the same orange secret. 小题1: Bruce wanted a carrot because he thought _______. A. he liked it B. it could help him see in the dark C.  it was sweet and delicious 小题2:How does vitamin A help your eyes work? A. The special chemical can stop your eyes from using up vitamin A. B. The special chemical is used to make Vitamin A which turns the light into messages C. Vitamin A is used to make the special chemical which turns light into messages. 小题3: Which of the following is NOT true according to the passage? A. Carrots are orange because they store beta-carotene. B. Any food which is orange or red must have some Vitamin A. C. Most fruits that are orange or red store some beta-carotene or Vitamin A. 小题4: Sweet vegetable, red peppers, and mangoes don’t have the same orange secret, do they? A. No, they don’t.     B. Yes, they do.     C. I’m not sure. 小题5: The passage mainly tells us that _______. A. we can’t see in the dark unless we eat many carrots every day B. we can’t see unless we eat a lot of orange or red food every day C. we should eat some food containing vitamin A so that we can see well
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【单选题】根据用途,弹簧钢与轴承钢属于( )。
A.
合金工具钢
B.
中合金钢
C.
合金结构钢
D.
特殊性能钢
【简答题】两个匝数相同的铁心线圈,分别接到电压值相等,而频率不同( f 1 >f 2 )的两个交流电源上时,分析两个线圈中的主磁通谁大谁小?
【简答题】两个匝数相同(N 1 =N 2 )的铁心线圈,分别接到电压值相等(U 1 =U 2 ),而频率不同(f 1 >f 2 )的两个交流电源上时,试分析两个线圈中的主磁通Φ 1m 和Φ 2m 谁大谁小(分析时可忽略线圈的漏阻抗)。
【单选题】一般来讲,硫、磷属于钢中的有害元素,应限制其含量,但在某些特殊用途的钢中,反而要适当提高其含量,主要是为了提高钢材的( )
A.
淬透性
B.
纯净度
C.
焊接性
D.
可加工性
【多选题】按照钢材的用途划分,()属于特殊钢。
A.
不锈钢
B.
耐酸钢
C.
碳素结构钢
D.
耐热钢
E.
磁钢
【简答题】两个匝数相同(N 1 =N 2 )的铁心线圈,分别接到电压值相等(U 1 =U 2 )而频率不同(f 1 >f 2 )的两个交流电源上时,试分析两个线圈中的主磁通画Φ 1m 和Φ 2m 的相对大小(分析时可忽略线圈的漏阻抗)。
【单选题】不属于钢按用途分类的是( )。
A.
建筑钢
B.
普通钢
C.
结构钢
D.
特殊性能钢
【单选题】一般地说,P、S属于钢中的有害元素,应限制其含量。但在某些特殊用途的钢中,却反而要适当提高其含量,以提高钢材的()。
A.
淬透性
B.
纯净度
C.
可焊性
D.
切削性
【单选题】9) Based on our understanding of the labor market model, we know that a reduction in the markup will cause
A.
an increase in the natural rate of unemployment.
B.
an increase in the equilibrium real wage.
C.
a reduction in the natural rate of unemployment and no change in the real wage.
D.
a reduction in the equilibrium real wage.
【单选题】特殊用途钢属于( )。
A.
碳素钢
B.
合金钢
C.
轴承合金
D.
有色金属
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