Final answer:
Ethanol requires an explosion-proof refrigerator for safe storage due to its flammable nature; other listed chemicals such as sodium chloride, hydrochloric acid, and calcium chloride do not pose this risk.
Step-by-step explanation:
When considering the storage of samples in a refrigerator, one must account for any potential explosion hazards. Of the listed chemicals, ethanol requires an explosion-proof refrigerator due to its flammable nature when in vapor form. This makes it a significant explosion risk at room temperatures and pressures. Storage of such chemicals in standard refrigerators could result in an explosion due to the presence of electrical sources that could ignite the fumes. Conversely, sodium chloride, hydrochloric acid (6.0 N, aqueous), and calcium chloride (desiccant) do not pose such risks and can be safely stored in a standard laboratory refrigerator.