Final answer:
The prefix anti-, as used in the word antisocial, means opposing. It indicates a behavior that goes against social norms or standards.
Step-by-step explanation:
The prefix anti-, as used in the word antisocial, most nearly means opposing. This prefix is commonly used in English to indicate opposition to or the inverse of something.
For example, 'antisocial' implies a behavior that is against or opposed to social norms, 'antithesis' indicates something that is the direct opposite of another thing, and 'antibacterial' describes a substance that opposes bacterial growth. So, the correct answer to the student's question is (b) opposing.