Final answer:
The African and South American Plates are expanding due to divergent boundaries, while the Pacific Plate is shrinking as it's consumed by subduction. The San Andreas Fault is a transform boundary between the Pacific and North American Plates, causing Los Angeles to move northward relative to San Francisco.
Step-by-step explanation:
Regarding the question of which two plates are growing in size and which plate is shrinking, the correct answer is A: The African Plate and the South American Plate are growing in size, while the Pacific Plate is shrinking. The African Plate and the South American Plate are increasing in size due to divergent boundaries where continental rifting is occurring, like the mid-Atlantic Ridge where these two plates are moving apart. On the other hand, the Pacific Plate is shrinking because it is subducting beneath other plates and the creation of new crust at its divergent boundaries is not as significant as the area being lost to subduction.
The San Andreas Fault is a transform boundary where the Pacific and North American Plates slide past each other. This motion suggests that the distance between San Francisco and Los Angeles is slowly increasing as the Pacific Plate moves northward carrying parts of southern California with it. Consequently, Los Angeles is on the Pacific Plate and is moving northward relative to San Francisco, which is on the North American Plate.