题目

I think that “狗带” must be one of the hottest words on the Internet this year, but I don’t know ____________. A. what does it mean               B. how it became popular C. whom was it first used by      D. why do people like using it 答案：B许多因素会影响化学反应速率。请分析下列实验或事实，分别说明在其他条件不变时，这些因素是如何影响化学反应速率的。示例:硫在纯氧中燃烧比在空气中进行得更快，更剧烈。答:增大反应物浓度，可以加快化学反应速率。（1）同种食品在夏天比冬天更容易变质_____。（2）过氧化氢溶液在常温下能缓慢分解，若加入少量MnO2时分解加速_____。（3）煤粉比煤块燃烧更剧烈_____。