What type of propagation may allow a weak high frequency (HF) signal to be heard at a distance too far for ground-wave propagation but too near for normal sky-wave propagation?

The region that is too far for ground-wave propagation but too near for normal sky-wave propagation is known as the 'skip zone' or 'dead zone'. Under normal conditions, no signal is heard in this area because the ground wave has faded out completely and the sky wave bounces entirely over it. Scatter propagation allows communication in this dead zone by redirecting a small amount of the transmitted signal back into it. Tropospheric scatter is generally a VHF/UHF phenomenon rather than HF, and Sporadic-E creates strong short skips rather than filling the dead zone with weak signals, making 'Scatter' the only correct choice.