According to OSHA regulations, posted warning signs ___ required in an area when lasers are in use.

• A. Are Not
• B. Should Be
• C. Must Be Posted
• D. Are

Answer: (D)

OSHA requires warning signs to be posted in areas where lasers are in use. The sentence is making a general rule, so the verb should express a present, ongoing requirement. Filling the blank with the word that fits this tone yields: “posted warning signs are required in an area when lasers are in use.” This phrasing clearly states the mandatory nature of the requirement. Saying “Are Not” would negate the rule, “Should Be” softens it instead of stating a firm requirement, and “Must Be Posted” is grammatically awkward in this exact sentence structure—the standard way to express the rule in OSHA-style statements is to say that something “are required.”