魏、蜀、吴三国建立的先后顺序是[ ]
A．魏、吴、蜀
B．蜀、魏、吴
C．吴、蜀、魏
D．魏、蜀、吴
答案：D
It is thought that one billion people in the world,_____ is half the world’s workers, earn their living by farming.
A．if
B．that
C．which
D．what
在发现法教学过程中，教师的主要任务是什么
