Which statement best describes allowable refrigerated storage temperatures for a 4°C sample?

• A. -20°C to -10°C.
• B. 0°C to 4°C.
• C. 0.5°C to 6°C.
• D. 15°C to 25°C.

Answer: (C)

Refrigerated storage means keeping the sample cold but not frozen, with a small tolerance to avoid ice formation or warming. For a sample designated to be stored around 4°C, you want a buffer that stays above freezing and well below typical room temperatures. The range 0.5°C to 6°C provides that safe window around 4°C, preventing freezing while avoiding warmth that could accelerate degradation. The other ranges involve freezing (-20 to -10°C), borderlines at or near freezing (0 to 4°C), or room temperature (15 to 25°C), none of which fit refrigerated storage for a 4°C sample.