题目

下列物质与空气混合，接触到明火，有发生爆炸危险的是（） ①氦气②氢气 ③一氧化碳④液化石油气⑤面粉粉尘 A . ①②③④ B . ①②③⑤ C . ②③④⑤ D . ①②④⑤ 答案：C________ is often the case with children, Tom was completely better by the doctor arrived．A.ThatB.WhatC.HowD.As