The correct option is A Both A and B are true and A is the correct reason for the occurrence of B.
Most of the coast along the Atlantic Ocean lies underwater. The eastern coast of North America has a lot of swamps and marshes. River mouths and bays also indent it. Because of these breaks or indentations on the coast, the eastern coast of North America has many important seaports. Ports of New York and New Jersey, Port of Virginia, Port of Charleston, and Port of Savannah are a few of the examples of important seaports situated on the eastern coast of North America.