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问题 选择题

用弹簧测力计在水平方向上拉动一个置于地面的物体，使它做匀速直线运动时，弹簧测力计的示数为5N，当弹簧测力计的示数为6N时，物体运动时受到的摩擦力大小是   [ ]

A．6N      

B．5N      

C．1 N     

D．11 N

答案

答案：B

单项选择题

It’s not easy to be an astronaut’s son. Everybody expects you to be special or perfect. I often wonder how my father ever had a son like me. I mean he’s so special and so good at everything he does. Even in middle school he was class president and captain of the football team.
Well, to be honest, I often dream about being some kind of hero or doing something special-like saving a child from a burning building or discovering a new star. I was daydreaming at school one morning when my teacher said there would be a Father’s Day writing competition for the whole school. "I hope we have a winner right here in my class. "
When I got home, I started to think about what to write. My father is an astronaut. No, I wouldn’t start like that. That was the way others saw him. How did I see my father Hmm.
I saw him sitting with me in the dark when I had a terrible dream. I remembered how he hugged me for hours when my dog Spotty was killed by a car. Yes, these were the things I was going to write. To me, he wasn’t just a world-famous astronaut. He was my dad.
My parents and I went to school Thursday night. There were so many people in the big hall! My dad looked at me, and I shrugged (耸肩).
The third prize was announced and it was not me. I was relieved (释然) and disappointed at the same time. The second prize was announced. It was me.
I went up to the stage and read what I had written, My Father’s Son. When I finished, the people stood up and cheered. I saw my father blowing his nose. Tears were running down my mother’s face. Dad cleared his throat and put his hand on my shoulder. "Son, this is the proudest moment of my life. "
It was the proudest moment of my life, too. Maybe I’ll never be a great hero or win a Nobel Prize, but it was enough just to be my father’s son.

What did the boy probably write in his composition ______

A. A lot of special things he had done.
B. The story of his father as an astronaut.
C. The unforgettable time he spent with his father.
D. The experiences his father had in middle school.
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单项选择题

有关主动脉，以下哪项不对（）

A.主动脉根部与左室相连

B.主动脉根部膨大称为主动脉窦，又称乏氏窦

C.主动脉窦分为右前窦、右后窦及左后窦

D.三个窦内各有一支冠状动脉开口

E.冠状动脉开口于窦壁中部
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