题目

根据对话内容，从对话后的选项中选出能填入空白处的最佳选项， 选项中有两项多余选项。—Officer, officer, I’ve something important to report, and you must help me. —OK. But before you start, why not take a seat and calm down a little? —You’re completely right. You see,     1    —Well, could you please tell me some details? —Where should I begin? —    2     Could you tell me when it took place? —About ten minutes ago. —And where was it? —Probably on the moving stairs coming up from the underground at Sidan.    3    将等物质的量的A、B混合于2 L的密闭容器中，发生如下反应： 3A(g)＋B(g)xC(g)＋2D(g)，经5 min后，测得D的浓度为0.5 mol/L，c(A)∶c(B)＝3∶5， C的平均反应速率为0.1 mol/(L·min)。通过计算求： （1）反应开始前容器中的A、B的物质的量； （2）B的平均反应速率； （3）x的值。