Questions: A closed sac with a distinct membrane that contains fluid is called a(n): (A) comedo. (B) abrasion. (C) furuncle. (D) cyst. (E) carbuncle.

The answer is (D): cyst.

Explanation for each option: (A) Comedo: This refers to a clogged hair follicle (pore) in the skin, commonly known as a blackhead or whitehead, and does not involve a distinct membrane containing fluid.

(B) Abrasion: This is a type of wound caused by superficial damage to the skin, such as a scrape, and does not involve a closed sac with a membrane.

(C) Furuncle: Also known as a boil, this is a painful infection of a hair follicle and surrounding skin, filled with pus, but it is not typically described as a closed sac with a distinct membrane.

(D) Cyst: This is a closed sac with a distinct membrane that contains fluid, semi-solid, or gaseous material. It fits the description given in the question.

(E) Carbuncle: This is a cluster of boils (furuncles) that are connected to each other under the skin, and while it involves pus, it is not a single closed sac with a distinct membrane.

In summary, the correct answer is (D) cyst, as it accurately describes a closed sac with a distinct membrane containing fluid.