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:

The text describes how bacteria on the skin feed on dead skin cells and skin - gland secretions, and in return, keep the skin moisturized and wounds safe. This shows benefits for both the bacteria (organisms) and humans, which is a mutual relationship. "Erratic" means unpredictable, "synthetic" means artificial, and "transient" means temporary, none of which fit the context.

Answer:

C. mutual