Against.

• A. -anti-
• B. -tri-
• C. -osis
• D. -stenosis

Answer: (A)

This item tests recognizing a prefix that conveys opposition. The form that means against is -anti-. When you attach it to a root, it signals that something works against or counteracts the root concept, as in antibiotic (fights bacteria), anti-inflammatory (reduces inflammation), or antiviral (acts against viruses). The meaning “against” is built into the very idea of anti-.

The other affixes don’t express opposition. -tri- is a numeric prefix meaning three, used in terms like triangle or triglyceride. -osis is a suffix that turns a root into a noun describing a condition or abnormal state, such as diagnosis or dermatitis. -stenosis denotes narrowing of a passage, a specific type of condition, rather than opposition. So the prefix that best captures the sense of “Against” is -anti-.