Question

read the paragraph, then choose the word that best completes the sentence. there is a zoo of critters living on the surface of ones skin—bacterial critters, that is. scientists have long known that healthy skin hosts bacteria, but a recent study revealed that this miniscule community is far larger and more diverse than first realized. invisible to the naked eye, trillions of bacteria, fungi, and other microbes naturally coexist. these organisms feed on dead skin cells and the secretions on the skin produced from glands. this is not a bad thing. according to genetics specialist julia segre, most bacteria are helpful. they keep the skin moisturized and wounds safe from other, more harmful, bacteria. the benefits to organisms and humans are ______. a erratic b synthetic c mutual d transient

Explanation:

To solve this, we analyze the context and the meaning of each option:

• Option A: "erratic" means unpredictable or irregular. The benefits described (bacteria helping skin, organisms getting nutrients) are not erratic. Eliminate A.
• Option B: "synthetic" means artificial or made by synthesis. The benefits are natural (from coexisting organisms), so B is incorrect.
• Option C: "mutual" means shared or reciprocal. The organisms get nutrients (from dead skin cells, etc.), and humans get benefits like moisturized skin and wound protection. This is a mutual benefit.
• Option D: "transient" means temporary. The relationship and benefits are ongoing (natural coexistence), so D is wrong.

Answer:

C. mutual