Just after putting the baby onto bed, Mrs. White suddenly caught sight of the pet cat and didn’t know how long it________ on the table for the family dinner.

A．had been laying; lying

B．had been lying; laid

C．had been laid; laid

D．had lain; laying

数据通信速度最快、安全性最好、出错率最低的硬介质是( )。

A．光缆

B．—无线电或微波

C．同轴电缆

D．双绞线