Which about Time Division Multiplexing is
题型：单项选择题
问题：
Which about Time Division Multiplexing is true ( )
A．TDM can only transmit digital signals
B．TDM divides the time that is used to transmit signals by channel into several time fractions and each user get a time fraction
C．Synchronous TDM may allocate channel time fraction dynamically
D．TDM can only transmit analog signals