Constrain (second occurrence) most closely means:

• A. To restrain; to limit
• B. To keep back; to confine
• C. To force; to oblige
• D. To hinder progress

Answer: (B)

Constrain is about restricting movement or freedom by placing boundaries or limits. The best match is the sense of keeping back and confining within limits, because it directly expresses the idea of imposing restrictions on someone or something. While constrain can also mean to force or oblige in some contexts, the core notion most closely tied to the word is setting boundaries that hold back or confine. Hindering progress can be a result of those restrictions, but it’s not the precise definition itself.