The correct is - (b) the African plate is spreading apart to form two separate plates.
The African tectonic plate, on of the biggest ones, but it will not be like for a long time in the future as the plate is separating into two parts. The eastern part of the plate is moving towards east, and it is moving away from the mainland Africa. Because of this movement, cracks have been forming all over the eastern side of Africa, thus the numerous faults. Over time, as the distance is increasing, the space in between will fill with ocean water, thus making a natural barrier between them, as well as setting the foundations for the creation of a new sea, or maybe even an ocean.
