题目

下列变化一定属于化学变化的是（ ） A．固体碘受热后变成紫红色碘蒸气      B．打开浓盐酸瓶盖，从瓶口涌出白雾 C．分离液态空气获取氧气    D．澄清石灰水露置空气中后液面产生了一层白膜 答案：DAfter the new equipment was introduced，they produced ________machines this year as the year before. A．as twice many          B．as many twice C．twice as many          D．twice many as