在a.单质、b.氧化物、c.酸、d.碱四类物质中，经一步反应可以生成盐的是[ ]
A．只有abc
B．只有cde
C．只有abd
D．abcd
答案：D
木材的基本密度是绝干材重量与气干材的体积之比。
—Was it not until last week（）he decided to give up smoking —No. He began（）he saw the news film last month.
A. when as soon
B. that immediately
C. did that
D. that till
