One effect that plentiful harvests had on ancient civilizations of the mainland's river valleys was to help have larger populations and the need to have materials to survive.
Answer:
D disruption of hibernation or migration cycles
Sleet is snow that melts and refreezes before reaching the ground creating a somewhat snowy surface
Freezing rain is snow that melts and refreezes once it hits the ground creating and icy surface like black ice or something
