This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
True stereopsis is perceived due to the following- 
Select and explain. 
A. Overlay of contours, B. Motion parallax, C. Bi- nasal disparity, D. Linear perspective
C: Bi- nasal disparity
Answer: C: Bi- nasal disparity 
Explanation: Stereopsis is defined as the relative ordering of visual objects in depth, that is, in the third dimension.
It will be very lengthy to explain the physiology of stereopsis here. You remember following facts about stereopsis:-

It is the visual perception of three dimensions during binocular vision.
Nasal disparity (binasal disparity) gives the impression of remoteness of an object.
Temporal disparity (bitemporal disparity) gives the impression of nearness of an object.