Which of the following examples listed below illustrates homeostasis maintained by a negative feedback?

a) production of vitamin d initiated by the suns uv light striking the skin.
b) formation of cerumen wax to deter insects from entering the ear.
c) thickening of epidermis to form a callus in places where the skin is exposed to friction.
d) changes in the response of the hair follicle to dihydrotestosterone (dht).

The right answer to this question is option D. Changes in the response of the hair follicle to dihydrotestosterone

   First of all, what is a negative feedback? Well, it's something that happens when there's a lot of something inside your blood, this "something" could be a hormone for example.

   But what does the negative feedback do to your system? That's simple, for example, if there's too much of a hormone, your blood will take that into the place where it was made in the first place, and that's how your body will know that you don't need that hormone to be produced anymore, because once that happens, a signal is send to your brain that warns it that that hormone is not needed anymore, then the production stops or slows down.

   So, about the question, option D is the right one just because of that, the body is producing a lot of a hormone, in this case it's dihydrotestosterone, and the brain recognized it after this hormone reaches the right point, and then the production slows down.

C: Thickening of epidermis to form a callus in places where the skin is exposed to friction.

Explanation:

I actually did the homework and tried the answer provided here it was incorrect. I then tried this one and it was correct therefore C is the correct answer.

the dna molecules have a negative charge because of the phosphate groups in their sugar-phosphate backbone, so they start moving through the matrix of the gel towards the positive pole. power is turned on and dna fragments migrate through gel (towards the positive electrode).

explanation: