Biological hazard sign is indicated by which color and lettering?

• A. Yellow sign red letters
• B. White sign black letters
• C. Blue with red letters
• D. Green sign white letters

Answer: (C)

Biological hazard signs rely on clear, high-contrast lettering so the warning is read quickly and understood as a danger. The most effective choice among the options is the blue sign with red lettering because red text against a blue background stands out the most and signals a warning clearly to anyone nearby. The other color/lettering combinations are either less legible at a distance or associated with different kinds of messages (caution, safety equipment, or safety guides) rather than a direct hazard warning. In standard practice you’ll often see biohazard signs on orange with black lettering, but within these choices, blue with red offers the strongest immediate visibility for a warning.