发电机阻力矩与机组转向和水轮机动力矩的方向（）。
A、相同；
B、相反；
C、无关；
D、垂直。
参考答案：B
-Have you got the airplane tickets?
-No, because it's May Day ,all the tickets to Beijing______out.
A．have been sold
B．had been sold
C．bad sold
D．were being sold
文件应满足哪些基本要求？
