题目

What a pity! I missed meeting my boss at the airport because my car was ___in the traffic jam．        A．broken up B．kept away C．held up     D．kept up 答案：B已知氧化还原反应反应 K2Cr2O7+14HCl═2KCl+2CrCl3+3Cl2+7H2O，关于该反应的说法中正确的组合（　　）①氧化剂是K2Cr2O7　                ②还原性：Cl-＞Cr3+③每生成1mol Cl2，电子转移为6mol　  ④CrCl3是氧化产物． A、①②B、①②④C、①③④D、①③