As one walks into a brightly lit room, the black structure in the center of one's eye seems to shrink to a tiny black dot. This response is caused by the action of the eye structure called the:

Iris

Explanation:

The Iris is a circular, thin structure present in the eye.The main function of the Iris is to control the size and diameter of the pupil.The Iris is also responsible for the amount of light reaching the retina.The colour of the eye is defined by the Iris.The iris is made up of smooth muscle fibers, connective tissue and pigments.

Carbon dioxide is the correct answer

Volcanoes make new rocks so not ahotspots are the the stuff that makes volcanoes mid atlantic ridge(mar cause i’m lazy) is a constructive plate boundary so it makes sense that new rocks would be found near it, also the mar is in the middle of the ocean so it fits the description deep ocean trench, umm, there’s no ocean trenches to where you’re goingso the mar is most likely the answeri wouldn’t trust me but hey why not