Which prefix means 'against'

• A. con- or com-
• B. extra-
• C. circum-
• D. anti-

Answer: (D)

Anti- expresses opposition or counteraction, attaching to a root to mean “against.” It shows up in words like antibiotic (fights bacteria) and antisocial (goes against social norms), and even antifreeze (prevents freezing). This sense of opposing or resisting is what makes anti- the correct prefix for “against.” The other prefixes point in different directions: con- or com- means with or together; extra- means outside or beyond; circum- means around. They don’t convey opposition, so they don’t fit the meaning described.