Final answer:
The narrow plains region is called the Tropical Plantation Region. It has a tropical climate and is known for its agricultural economy.
Step-by-step explanation:
The narrow plains region located between the Brazilian Highlands and the Atlantic Ocean is called the Tropical Plantation Region. This region, which extends along the north and east coast of South America, has a tropical climate and is known for its agricultural economy. In the colonial era, Europeans established plantations in this area, with a large population of African and Asian descent.