Which prefix signifies 'Against'?

• A. Semi-
• B. Exo-
• C. Contra-
• D. Ultra-

Answer: (C)

Opposition is signaled by the prefix that means “Against.” The prefix contra- conveys opposition or counteraction. In medical terms you see it in words like contraindication (a condition that makes a treatment inadvisable) and contraception (against conception). The other prefixes don’t carry the sense of opposition: semi- means half or partial, exo- means outside, and ultra- means beyond or excessive. So contra- is the best fit for indicating “Against.”