题目

用氧化物X测定空气受CO的污染的程度，发生化学反应的方程式为：X+5CO=I2+5CO2根据CO2的多少，可测定CO的含量，则X的化学式为________ 答案：I2O5  I don’t understand _________ that everything’s fine when it’s not. A. how can he say                       B. can he say how C. he can say how                       D. how he can say