16 d overlap (In monocular cue, when one object obscures another, we can infer that the blocking object in closer than the blocked object).
17 d binocular disparity ( it occurs because of the difference between the retinal images of our eyes and how the differing signals influence the visual image perceived by our brain we have two eyes and two slightly different signals are sent to the brain because of slightly discrepancies in the retinal image)
18 d Relative size ( When two objects of the same size, the monocular cue states that if an object seems larger, it is probably closer, and if an object is smaller, it is probably distant).
19. b Texture Gradient (texture may play a role in helping us determine the size of an object when the texture units change in size then depth is indicated, in this the spaces are shaped so that the top is smaller than the bottom and the sides tilt in towards the middle).
20 Binocular Cues ( It depends upon using the two eyes, The greater the inward strain, the closer the object)
21 d, REM sleep, ( REM is the stage of sleep when the brain is very active and the person often sees the dream in this stage, the body is unable to move except the eyes and muscle that are used in breathing).