问题 选择题
电气化铁路的输电线常用图所示的方式悬挂在钢缆上.钢缆的A端固定在电杆上,B端连接在滑轮组上.滑轮组由a、b、c三个滑轮构成,配重P由多个混凝土圆盘悬挂在一起组成,配重的总重为G,若不计摩擦和滑轮的重量,则以下说法中正确的是(  )

A.a为动滑轮,B端钢缆受到滑轮组的拉力大小约为3G

B.a为动滑轮,B端钢缆受到滑轮组的拉力大小约为G

C.a、c为动滑轮,B端钢缆受到滑轮组的拉力大小约为3G

D.a、c为动滑轮,B端钢缆受到滑轮组的拉力大小约为G

答案

答案:A

问答题

When Dan Shaw gets up from the sofa in his home, Cuddles is never far away. When he wants to go outside, he doesn’t take Cuddles out for walk—Cuddles takes him for a walk. Cuddles is clearly no ordinary family pet. It is a two-foot-high miniature horse and serves as the guiding eyes of Shaw, who is blind.

When Shaw lost his sight, his wife suggested he apply for a guide dog. Shaw, an animal lover, said he couldn’t bear to part with a dog (which usually lives about eight to ten years) and get used to a new one, perhaps several times in his life.

Then Shaw heard of a program about the tiny guide horses. He learned that the horse possess many qualities that that make them an excellent choice for guiding people. They are clean friendly, smart and have great memories. They can be trained to remain calm in noisy and crowded places. Best of all, they live for 25-25years, which would enable Shaw to have the same guide companion for most or all of his life.

Shaw immediately applied to be and was accepted as the first person to receive a guide horse. The instant he met Cuddles, he knew he was making the right choice. Then he began his training.

Through training ,Shaw and Cuddles learned to find way on busy streets, step over curbs(便道沿儿)and find elevator buttons. Cuddles even demonstrated(显示)its ability to step in front of Shaw and block him, to prevent him from walking into a dangerous situation. The little horse also expertly led Shaw through busy shopping malls. They got along without any difficulties. Now Shaw is confident that Cuddles will change his life for the better.

What does Paragraph 3 mainly tell us (No more than 10 words)

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