Which term demonstrates the prefix 'eu-'?

• A. Eupnea
• B. Euclid
• C. Eustachian
• D. Europe

Answer: (A)

The prefix eu- means good, true, or normal. When attached to a root that denotes a process, it signals a normal or well condition. In eupnea, pnea means breathing, so eupnea literally describes normal breathing. That direct link between eu- and a medical root shows how the prefix modifies the meaning to “normal,” which is exactly what the question is asking you to recognize.

The other terms are not formed from a prefix + medical root in this sense. They are proper names or terms named after people (or places) rather than a prefix indicating a normal state. Eurclid and Europe come from historical names, and Eustachian is a person’s name used in anatomy, not a constructed term using eu- plus a medical root.