ATM信元信头中，HEC字节只对（）进行差错控制，在网络中不对用户信息进行差错控制操作。
参考答案：信头
The foreigner was talking to the children in the park ______ he was familiar with them.[ ]
A. even though
B. in case
C. so that
D. as if
脉象表现为沉按实大弦长的脉是（）。
A．牢脉
B．伏脉
C．代脉
D．洪脉
