Which sentence correctly uses prohibit?

• A. The sign prohibits to smoke in the building.
• B. The sign prohibits smoking in the building.
• C. Smoking is allowed in the building.
• D. Visitors may smoke in designated areas.

Answer: (B)

The main idea here is how the verb prohibit pairs with its object. After prohibit, English uses the gerund form to name the action being forbidden. So the correct sentence says the sign prohibits smoking in the building, with prohibit + smoking. Using an infinitive, as in prohibits to smoke, is not standard after prohibit. The other options either misapply the verb form or express a different policy (saying smoking is allowed, or describing permission for visitors), which don’t demonstrate the correct prohibition structure.