在飞行中，当选择计划方式时，（）。
A.飞机随着飞行计划移动
B.显示磁北方向
C.无气象雷达信息显示
D.显示飞行计划
参考答案：A, C, D
环境与自然经济学
— Did you know any Chinese before you arrived in Beijing?
— Never ________ it, actually.[ ]
A. had I learned
B. have I learned
C. I have learned
D. I had learned
