题干

图是常用指甲刀的实物及结构示意图,下列说法中不正确的是()

A:杠杆ABC是一个省力杠杆

B:杠杆ABC的支点是B

C:杠杆OBD是一个费力杠杆

D:指甲刀共有三个杠杆,一个省力杠杆两个费力杠杆

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答案(点此获取答案解析)

B

同类题2

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    A little boy invited his mother to attend his school's first teacher-parent meeting. To the little boy's dismay(沮丧), his mother said she would go. This would be the first time that his classmates and teachers met his mother and he was embarrassed by her appearance. There was a severe(严重的) scar (伤疤) that covered nearly the whole right side of her face. The boy never wanted to talk about why or how she got the scar.

    At the meeting, the people were impressed by the kindness of his mother with the scar, but the little boy was still embarrassed and hid himself from everyone. However, he could hear clearly the conversation between his mother and the teacher.

     “How did you get the scar on your face?” the teacher asked.

    The mother replied, “When my son was a baby, he was in a room that caught on fire. Everyone was too afraid to go in because the fire was out of control, but I went in. As I was running towards his bed, I saw a burning wood falling down and I placed myself over him trying to protect him. I was knocked to be unconscious(无知觉的), but luckily, a fireman came in and saved both of us.” She touched the burned side of her face. “This scar will be forever, but until today, I have never regretted doing what I did.”

    When the little boy heard this, he couldn't help running towards his mother with tears in his eyes. He hugged her and felt his mother was greater than anyone. He held her hand tightly for the rest of the day.