Which prefix indicates a positive or normal state?

The prefix that indicates a positive or normal state is found in "eu." This prefix is derived from the Greek word "eu" meaning "good" or "well." In medical terminology, it conveys a sense of normalcy or health. For instance, in terms like "euthyroid," it indicates a normal functioning thyroid gland.

In contrast, the other prefixes have different meanings. "Oligo-" refers to a deficiency or a small amount, as seen in conditions like "oliguria," which indicates a reduced urine output. "Hypo-" implies a below normal level or deficiency, commonly used in terms like "hypoglycemia," meaning low blood sugar. "Inter-" typically refers to something occurring between, such as "intercellular," indicating processes or structures that exist between cells.

Thus, the prefix "eu" distinctly and positively signifies a normal state in medical terminology, making it the correct choice for this question.