Friday Morning Trivia (or Tuesday Night Trivia on Friday Morning)

This trivia challenge is a replacement for this week's Tuesday Night Trivia, in which I made an embarrassing error. Thus, the Tuesday Night Trivia graphic.

Here's the replacement challenge:

In the Western Hemisphere four pairs of neighboring countries have names that begin with consecutive letters. Name them.

To clarify: If Canada (C) and Dominica (D) shared a border, they would be the fifth pair. Also: Maritime borders don't count. (That would make things way too complicated.) So Bahamas and Cuba are not one of the pairs.

Hint: Two countries are part of more than one pair.