A tank has been sealed and unventilated for a long period of time. Which of the following statements is true?

Correct Answer: Option B — The tank is especially dangerous to enter.

Sealed, unventilated tanks are hazardous due to potential oxygen depletion, the accumulation of toxic gases, or the presence of flammable vapors. Under 46 CFR and OSHA confined space entry standards, such spaces must be tested for atmospheric safety and properly ventilated before any personnel entry is permitted.