Which combining form means "out from"?

• A. Dromo
• B. Dys
• C. Ecto
• D. Echo

Answer: (C)

Understanding location-building terms helps you pick meanings like “out from.” The form ecto- signals exterior, outside, or external. It comes from Greek and shows up in words such as ectoderm (the outer layer of cells) or ectopic pregnancy (implantation outside the uterus). That sense of being on the outside is exactly what “out from” conveys, so ecto- is the best fit.

Dromo means running or a course, dys means bad or abnormal, and echo relates to sound or reflected sound in imaging. None of those indicate a directional meaning like outside or out from.