What is true about the coastal plain of North Carolina?

The coastal plain of North Carolina is indeed wide and relatively flat, which is characteristic of coastal plains around the world. This flat terrain is formed by the accumulation of sediment from rivers depositing soil and sand as they reach the ocean, creating a gentle slope typically running from inland areas down to the shore.

Additionally, the region was once covered by the Atlantic Ocean, particularly during different geological periods, such as the Cretaceous period. This historical exposure to marine conditions contributed to the sedimentary deposits that constitute the coastal plain today. As a result, fossils and geological formations found in the area can often be traced back to this earlier time when the sea extended over the land.

These characteristics combine to make both statements about the coastal plain true, thereby confirming that the correct answer includes both features of the terrain and its geological history.