题干

在探究重力势能与物态质量的关系时,实验桌上有大小不同的实心铁球和大小不同的实心木球若干.老师提出了一个问题:“一个静止在高处的物态有多大的重力势能,我们无法直接观察到.那么,怎样才能判断它的重力势能大还是小呢?”于是同学们开始了讨论.下面是小明和小敏关于这个问题的讨论.

小明:让大小不同的铁球从相同高度落向沙坑,观察留下的凹痕,留下凹痕深的重力势能大,反之说明重力势能小.

小敏:如果两个大小不同的铁球从同一高度落下,大铁球可能会停留在沙的表面,小铁球可能陷入沙的里面,这是否说明小铁球的重力势能更大?老师说小敏的质疑是有道理的.

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阅读下面短文,从每题所给的A、B、C和D四个选项中,选出最佳选项。

B

    Two weeks before my 12th birthday, my teacher asked me to conduct an experiment. When I mixed some powder together, they exploded. Molten liquid hit me in the face, but I felt no pain.

    I vividly remember standing there in a state of calm. I thought I was in a dream, but however hard I struggled to swim to the surface of consciousness, I couldn't wake up. I didn't understand how terrifying it was until I heard people saying, "Who's that?" That's when I knew I was unrecognizable.

    I was taken to hospital, but the doctors didn't know what to do with me. Later I was flown to Houston for surgery. Between the ages of 13 and 16, I had 40 operations. As each operation came and went, my vision would come back, then fade again. Eventually, it faded completely and I had what was left of my eyes removed for cosmetic reasons.

    Since then, I have lived in total darkness. Most blind people, even if they don't have any sight they're aware of, are still able to sense light. That gives them a sense of day and night. But not me. I absolutely lost that sense of time passing.

    For many years, I felt my sight loss darkening my life like the loss of my parents from which I would never recover. But when I was in my 40s, I realized I had to find a way to live. I trained to become a counselor, and that has helped me see my experiences in a different way. I can't fix people's broken lives — just like I can't fix my sight — but I can help them find a way to manage.

    Sometimes it feels as if all the struggles and negative experiences I've lived through were in fact a kind of preparation for helping others to make their own way towards the light.