STM也称为时分复用（TDM），不同设备和业务的比特流在传输过程中被分配固定的带宽
参考答案：对
窗体是数据库中用户和应用程序之间的主要界面，用户对数据库的______都可以通过窗体来完成。
I’d like to see you off at the airport. Could you tell me _____ ?
A．when your plane took off
B．when did your plane take off
C．when your plane takes off
D．when does your plane take off
