光分插复用器的简写是（）
A.OADM
B.ADM
C.ODF
D.DDF
参考答案：A
The year 1949 _____the birth of a new country---the People’s Republic of China.
A．watched
B．noticed
C．saw
D．recorded
液化石油气钢瓶是充装乙炔的专用容器。
