Q.Define skip zone

Between the reach of the ground wave and the point where the sky wave lands, there is a region that receives no signal. …

[!TLDR]

The skip (silent) zone is the ring around the transmitter, within the skip distance, where no signal is received.

The ground wave fades out at some distance from the transmitter, while the sky wave does not return to earth until the skip distance is reached. Between these two — beyond the ground-wave range but inside the skip distance — lies a region where neither the ground wave nor the sky wave is present, so no signal can be received there. This is called the skip zon …