What type of cargo must be vented overboard during transport?

The correct choice focuses on cryogenic liquid storage and transfer tanks. These types of cargo contain materials that are stored at extremely low temperatures and can expand rapidly if allowed to vaporize. During transport, any excess pressure within the tank must be managed to prevent dangerous situations such as explosions. Vented overboard allows the gas to safely dissipate into the atmosphere rather than accumulating or posing risks inside the vehicle or storage area.

In comparison, general cargo typically consists of solid items that do not require special handling or venting. Liquid bulk cargo does not necessarily have to be vented overboard unless it contains specific hazardous substances. Hazardous waste may have regulations for handling but is generally not vented in the same way that cryogenic liquids might be, especially since hazardous materials often require containment and management according to specific regulations. Thus, the requirement for venting is particular to cryogenic liquids and their unique properties related to pressure and temperature control during transport.