Which type of tank is specifically used for transporting cryogenic liquids?

The correct choice is the type of tank specifically designed for transporting cryogenic liquids is referred to as MC 338. This designation is crucial because MC 338 tanks are built to handle the unique challenges presented by cryogenic materials, which are substances that exist in a liquid state at very low temperatures. These tanks are constructed with insulation to maintain the low temperatures necessary for the safe transport of cryogenic liquids, preventing heat from entering and causing the liquid to vaporize.

The design includes features such as double walls and vacuum insulation, which are essential for minimizing heat transfer. This ensures that the cryogenic liquid remains in its liquid state throughout transportation, thereby preventing hazards associated with pressure build-up and increased volatility that can occur if the liquid were to heat and vaporize.

In contrast, the other types of tanks mentioned have different uses that do not specifically address the requirements for transporting cryogenic substances. MC 312 is typically used for transporting corrosive liquids, MC 331 is used for high-pressure gases, and MC 307 is associated with flammable liquids. Each of these has its own design and specifications tailored to the properties of the substances they are intended to carry, which is why MC 338 stands out for cryogenic liquids.