题目

Why is Peter’s teacher angry with him? A.Because he was late. B.Because he fell asleep in class.C.Because he didn’t finish his homework. 答案：【答案】B【解析】【原文】略参考下列物质的微观结构图示，其中由原子直接构成的物质是（ ）A．     金B．干冰（固态二氧化碳）C．  氯化钠D．      金刚石