题目

They _______ to come to the meeting on time，but they were late again  A．meant    B．had meant    C．means    D．have meant 答案：B 解析: 略甲、乙、丙、丁四种物质(可以是溶液)中，甲、乙、丙均含有相同的某种元素，它们之间具有如下转化关系：。同下列物质不符合此转化关系的是A．甲为铁，丁为氯气 B．甲为碳酸钠，丁为盐酸C．甲为碳，乙为一氧化碳D．甲为氯气，丁为铁