清朝中期以后，中国在世界上逐渐落伍了，导致其落伍的主要原因是(    ）

阅读下列短文，从下面每题的A、B、C、D 四个选项中选出最佳答案。

    It happened many years ago, but I still remember it clearly. That day I was invited to work as a contest judge (评委) at a college. All of the students had been given a piece of paper with a topic on it. The first one to speak looked a little unhappy. “My fellow students and respected judges,” he said loudly, “this is an unfair (不公平的) contest!” “I have been given this paper,” he continued, “to speak on a topic with just a few minutes’ preparation while those coming after me have more time to work on their speeches!” He then left the stage and went out of the hall.

    I met him later by chance. “Who says life is fair?” I asked him with a smile, and I asked him to walk with me to my car. “Have you seen the numbers they show when a new car is being introduced into the market, saying how economic (经济的) it is?” “Yes,” he nodded “But they put a line after all these numbers. They say all the numbers are in ideal (理想的) road conditions!” “Yes,” he said again. “Can you show me some ideal road conditions?” I asked him，and he smiled. “The car that sells well is the one that will provide power and speed on the worst roads. That car is the winner!”

    We had reached my car. “Don’t look for ideal contest conditions,” I said. “Fight the unfair and come out a winner!”

    I looked back as I drove away and saw him smile and wave to me.

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