Large hemispherical heads on both ends of an uninsulated tank are characteristic of which type of cargo tank truck?

Answer: B — MC-331 high pressure carrier

Large hemispherical heads on both ends of a tank are a design feature specific to high-pressure cargo tank trucks, which includes the MC-331 classification. This shape helps to accommodate the stresses associated with the high pressures these tanks operate under, allowing them to safely contain gases that are compressed at high pressures, such as liquefied gases. The hemispherical design is optimal for these types of applications, as it distributes stress evenly across the tank structure, minimizing the risk of rupture or failure. This design is particularly important for the safe transportation of gases under pressure, ensuring they can handle the physical demands of such materials. In this context, the other types of cargo tanks do not typically feature this design. For instance, an MC-306 non-pressure carrier is specifically designed for transporting liquids under normal atmospheric conditions and would typically have a different head design. Similarly, an MC-338 cryogenic liquid carrier, while designed for specific types of cryogenic materials, does not focus on high-pressure containment in the same way as the MC-331. The MC-307 low pressure carrier also does not possess the necessary design features associated with high-pressure capabilities. Thus, the presence of large hemispherical heads identifies the tank as an MC-331 high pressure carrier.