飞机在飞行中可以作哪几个方向的运动()
A、俯仰运动和滚转运动
B、滚转运动和偏航运动
C、俯仰运动和偏航运动
D、俯仰运动、滚转运动和偏航运动
参考答案:D
Listen! His family must be quarrelling, ______
A. mustn't it B. isn't itC. aren't they D. needn't they