Context: Read the passage and look at the picture.
The Mid-Atlantic Ridge is a massive mountain chain that runs along the floor of the Atlantic Ocean. On this map, the ridge is shown by the light blue area between Africa and South America. The dark blue areas on either side of the ridge show deeper regions of the ocean.
The Mid-Atlantic Ridge began to form millions of years ago as the African Plate and the South American Plate moved away from each other. The plates are still moving apart at a rate of about 2.5 centimeters per year, causing the ridge to grow even taller and wider.
Complete the sentence.
The Mid-Atlantic Ridge formed at a () boundary.
A. divergent
B. transform
C. convergent
From the given choices, pick the correct answer and respond by indicating the letter of the correct option.

A