| 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 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  |
答案：A
| 根据对话内容，从对话后的选项中选出能填入空白出的最佳选项.选项中有两项为多余选项。 |
| —Lovely day, isn't it? —Mm, yes, 1 . And it's supposed to get warmer. —Yes, that's true. You know, though, I'm always a little worried to see winter go. — 2 . —Well, I love skating. In fact, I used to teach skating for a living. —Oh? That sounds interesting. 3 . —I work at Bank of America. How about you? — 4 . —Here? —No, I'm from Chicago. I'm just visiting here for the wedding. — Oh, I see. — By the way, 5 . I'm Helen Keller. —Nice to meet you. My name is John Smith. A. But what do you do now? B. It's very cold. C. It's really warm. D. I guess I should introduce myself. E. I'm on the radio station. F. What' your name? G. Really? |
G
G