For many years, people（）electric cars. However, making them has been more difficult that predicted.

A. had dreamed of

B. have dreamed of

C. dreamed of

D. dream of

下列关于煤、石油和天然气的说法正确的是（　　）

A．煤的干馏就是将煤隔绝空气在高温使之分解，得到焦炭、煤焦油等物质的过程

B．煤的气化就是将煤在高温条件由固态转化为气态的物理变化过程

C．天然气除了作燃料之外，还可用于合成氨和生产甲醇

D．石油分馏可获得乙酸、苯及其衍生物