题干

随着人们安全意识的加强,酒驾的危害也越发引起人们的重视。小林出于好奇设计了一种酒精气体浓度测试电路。图中R0为定值电阻,R为酒精气敏元件,其阻值随被测气体中酒精气体浓度的变化规律如图甲所示。小林希望随着气体中酒精气体浓度的增大,电表的示数也增大。若电源两端的电压不变,则闭合开关S后,如图中能够实现上述功能的电路是(    )


A:

B:

C:

D:

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B

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    One day a man found a cocoon(茧) of a butterfly in the forest. He sat there for several hours and watched the butterfly. Suddenly a small opening appeared, and the butterfly made its great effort to force its body through that little hole. Then it seemed to stop making any progress. It appeared as if it had gotten as far as it could and it could go no further.

    So the man decided to help the butterfly. He cut off the remaining bit of the cocoon so that the butterfly could come out easily. But to his surprise, the butterfly got a heavy body and very small wings when it came out of the cocoon.

    The man continued to watch the butterfly because he expected that the body would grow smaller at any moment and the wings would become larger and be able to fly. But neither happened! In fact, the butterfly spent the rest of its life crawling(爬) around with a heavy body and small wings. It was never able to fly.

    The man was in his kindness, but he did not understand the nature rules. Before the butterfly came out of the cocoon, fluid(流体) from its body must be forced into its wings, and then it would be ready for flying. It must have a hard struggle(拼搏) to get through the small opening to get its freedom from the cocoon.

    Sometimes struggles are exactly what we need in our life. If God allowed us to go through our life without any difficulties, it would make us fail. We would not be as strong as we could have been, we could never fly.