Final answer:
Size constancy is the recognition that an object's dimensions remain the same despite changes in its retinal image. It is part of visual perception and allows us to perceive the size of an object as constant even when the distance from the object changes. So, the correct answer is option a.
Step-by-step explanation:
The recognition that an object's dimensions remain the same even though the retinal image of the object changes as you move toward or away from the object is called size constancy. Size constancy is the ability of the brain to perceive the size of an object as constant even when the distance from the object changes. For example, if you see a car that appears smaller when it is far away, you still know it is the same size.
So, the correct answer is option a.