Answer: C. Macro-
Step-by-step explanation: A root word is the most basic part of a word, and it is the part that holds the main meaning. We are given four examples of root words, micro means small or tiny, an example of a word that uses "micro" is "microorganism." Dorm means sleep, and an example of a word with "dorm" is "dormitory." Mal means bad or ill, and example of a word using "mal" is "malicious." And finally, macro means large or long, an example of a word using "macro" is "macronutrients."