题干

A、B两球质量相等,A球竖直上抛,B球平抛,两球在运动中空气阻力不计,则下列说法中正确的是(   )

A:相同时间内,动量的变化大小相等,方向不同

B:相同时间内,动量的变化大小相等,方向相同

C:动量的变化率大小不等,方向相同

D:动量的变化率大小相等,方向不同

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B

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    One night, when I was eight , my mother gently asked me a question I would never forget. “Sweetie, my company wants to  1me but needs me to work in Brazil. This is like your teacher telling that you've done 2 and allowing you to skip a grade(跳级), but you'll have to 3 your friends. Would you say yes to your teacher?” She gave me a hug and asked me to think about it. I was puzzled. The question kept me 4 for the rest of the night I had said “yes” but for the first time, I realized the5decisions adults had to make.

    For almost four years, my mother would call us from Brazil every day. Every evening I'd 6 wait for the phone to ring and then tell her every detail of my day. A phone call, however, could never replace her 7and it was difficult not to feel lonely at times.

    During my fourth-grade Christmas break, we flew to Rio to visit her. Looking at her large 8 apartment, I became 9 how lonely my mother must have been in Brazil herself. It was then10 I started to appreciate the tough choices she had to make on 11 family and work. 12difficult decisions, she used to tell me, you wouldn't know whether you make the right choice, but you could always make the best out of the situation, with passion and a 13attitude.

    Back home , I 14 myself that what my mother could do, I could, too. If she 15  to live in Rio all by herself, I, too, could learn to be 16 . I learn how to take care of myself and set high but achievable17.

    My mother is now back with us. But I will never forget what the 18 has really taught me. Sacrifices 19 in the end. The separation between us has proved to be 20 for me.