能见度不良的在航失控船应鸣放（），周期不超过2分钟。
A、一长一短
B、二长声
C、一长二短
D、一长声
参考答案：C
My parents _____ in Hong Kong. They were born there and have lived nowhere else. [ ]
A. live
B. lived
C. were living
D. had lived
Use your head. nothing taught by others can have the same effect on you as ________learned by yourself．
A．those
B．what
C．that
D．the one
