Which feature distinguishes a MC-331 from other tank trucks?

The distinguishing feature of an MC-331 tank truck is its design, which resembles a bullet and is specifically engineered for transporting liquefied gases. This design is critical because it allows the tanker to maintain the pressure needed to keep these gases in a liquid state during transport. The MC-331's construction is optimized for carrying products such as propane, butane, and other similar gaseous substances that require specialized containment to prevent them from vaporizing and creating hazardous conditions.

The other options describe characteristics that do not apply to the MC-331. For instance, the MC-331 is not limited to carrying corrosive liquids, nor does it have a vacuum space between tanks; these aspects are associated with different types of tank trucks. Additionally, it is not designed for transporting dry materials, which further confirms its specific role in handling liquefied gases. Thus, the bullet-like shape and the functionality that comes with it are what set the MC-331 apart from other tank trucks.