我国数字卫星电视采用（）规范。
A.DVB
B.AVB
C.NTSC
D.ADSL
参考答案：A
_______ he was 12, Einstein had learned advanced mathematics by himself.
A．As soon as
B．At the time
C．By the time
D．During the time
在E-R图中，用来表示实体的图形是( )。
A) 矩形 B) 椭圆形 C) 菱形 D) 三角形
