Which root means circle?

• A. Circle
• B. Bladder, sac
• C. Down, from
• D. Tooth

Answer: (A)

The concept tested is identifying a root that carries the idea of circle. In medical terminology, the root is the base meaning of a term. The only option that directly expresses circle is Circle, which clearly signifies the circular concept. The other roots point to completely different ideas: bladder or sac is cyst- or vesic-, down or from is indicated by directional prefixes like de-, and tooth is dent- or odont-. So the circle meaning is the best match because it directly conveys the shape concept at the root level.