视频通话时会有一些延迟，因为声音和图像需要传输时间。

There's always a slight ___time-lag during video calls because sound and images take time to transmit.

视频会议时，网络延迟会造成明显的信号传输时间差。

During video calls, network latency causes a noticeable ___time-lag in signal transmission.