CLOUD FORMATION, he said it under the question but i put it here so it would be easier too find
Answer:
I don't know but it might be B

Which process was primarily responsible for the formation of coastal plains?
Answer:
A.) deposition of sediments by rivers Is The Correct Answer!
Layers of this deposited sediment build up over time, creating a flat or gently sloping landscape. Wetlands often dominate coastal plains.
Hope this helps!!
