题干

电磁打点计时器是一种使用低压____(填“直流”或“交流”)电源的计时仪器;若在实验时交流电源的电压突然减小且实验者并不知道,那么实验根据纸带上的数据计算某段时间内的平均速度值与实际值相比____(填“偏大”、“偏小”或“不变”).

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答案(点此获取答案解析)

交流,不变

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根据短文理解,选择正确答案。

    Terrible disasters in the last 50 or 100 years have become increasingly common. Over the last 30 years, the number of weather-related disasters has increased quickly, and the disasters have also affected more people and caused more economic loss. However, much of this could be avoided through disaster risk reduction(DRR降低灾难风险).

    A meeting, held in Sendai, Japan last month, opened one day after Cyclone Pam(飓风Pam)hit Vanuatu, which struck the islands with winds of up to 340km/h and destroyed the island nation. The speech by the President of Vanuatu was given shortly after that. He begged the international community for support and stronger commitment (承诺)to helping them manage climate and disaster risks. In the face of disasters, it is always the developing countries that suffer most. Damage in these countries is often worse and unluckily, there is limited money and technique to prevent these disasters.

    In fact, we have seen Asian countries-especially those that have suffered a lot in disasters can't pay the price. Great loss Asia has suffered comes to a total of almost $ 53 billon yearly over the past 20 years.

    At the same time, studies have shown once again that proper prevention saves lives and damage. With this in mind, people at the Sendai meeting were able to come up with new agreements that effective ways of disaster risk reduction will be carried out in the coming years for those who easily get damaged in disasters.