题目

If he ________ his teacher's suggestion, he would have won the English Speech Contest. A . had followed B . should follow C . was to follow D . followed 答案：A “绿色奥运”是北京2008年奥运会的主题之一．为减轻污染，北京市为汽车加装了“三效催化净化器”，可将尾气中CO、NO转化为参加大气循环的无毒混合气体，该混合气体可能是 [　　] A．CO2和NO2 B．CO2和O2 C．CO2和NO D．CO2和N2