Puerto Rico is a U. S. territory that is southeast of the mainland United States. Which letter on the map represents the location of Puerto Rico?

The letter that represents the location of Puerto Rico on the map is A.

As the question noted, Puerto Rico is to the southeast of the United States. The first step therefore, would be to find the United States.

The United States is located in the center of the map and is painted orange. I have highlighted it in the attachment.

A place that is southeast of the United States would be both:

The only place matching that description is labeled A so we can conclusively say that Puerto Rico is labeled the place labeled A.

For more information on Puerto Rico check

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).