The iris is a pigmented muscular curtain found near the front of the eye and between the cornea and lens. It is perforated by an opening known as the pupil. The location of the iris is found in front of the eye lens and the ciliary body and posterior to the cornea. It is bathed in a fluid called as the aqueous humor.
The iris consists of two sheets of smooth muscles with opposing actions: dilation/expansion and contraction/constriction. The primary function of these muscles is tho control the size of the pupil and modulates how much light reaches the sensory tissue of the retina. The sphincter muscle of the iris is a rounded muscle that constricts the pupil whenever there is a bright light, whereas the dilator muscle expands the eye opening when it contracts.
Therefore, the answer is D. SMOOTH AND INVOLUNTARY because first of all the types of muscles that comprises the muscles in the iris are smooth and it is involuntary because they eyes auto-regulates the light that comes to it without our conscious effort.
D) chromosomes exchange genetic material in step 3
Explanation: the student claims that the cell division increases genetic variation, and D) is the only one which mentions exchanging genetic material/increasing variation
