题干

对某动物细胞进行荧光标记实验,如下图所示,其基本过程:①用某种荧光染料标记该动物细胞,细胞表面出现荧光斑点。②用激光束照射该细胞表面的某一区域,该区域荧光淬灭(消失)。③停止激光束照射一段时间后,该区域的荧光逐渐恢复,即又出现了斑点。上述实验不能说明的是                                   (  )

A:细胞膜具有流动性

B:荧光染料能与细胞膜组成成分结合

C:根据荧光恢复的速率推算出物质跨膜运输的速率

D:根据荧光恢复的速率可推算出膜中蛋白质或脂质的流动速率

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答案(点此获取答案解析)

C

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完形填空

阅读下面短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项。

    On that particular day after I finished giving my training course, I took a flight home. Upon1the plane, I noticed a boy who was around eight years old, sitting in the window seat2 mine. Trying my best to be 3, I said “hello” and introduced myself, and he told me his name was Bradley. We started a4 and within minutes, he took me into his confidence, saying, “This is the first time I have ever been on a plane. I'm a little bit 5.” I managed to 6 him.

    As we ascended (上升), he looked out of the window and started describing excitedly everything he was 7. Then he told me he needed to go to the bathroom, 8 I stood up to let him out into the aisle. It was then that I noticed the brace (支柱) on his legs. Bradley, 9made his way down to the bathroom and back. Sitting back down, he 10, “I have muscular dystrophy(肌肉萎缩症), and so does my sister, who's in a 11 now.”

    As we descended (下降), he looked over, smiled, and spoke in a low, almost 12 voice, “You know, I was really13 about who would sit beside me on the plane. I was afraid it would be someone who didn't want to 14 with me. I'm so 15 I sat beside you.”

    16 the whole experience later that night, I was reminded of the17 of being open to the moment. Now when 18 get(s) rough, I look out of the window, try to see what images the clouds are painting in the sky, 19remember Bradley, the beautiful child who taught me that 20.