Final answer:
The identifying characteristic of a pressurized horizontal tank is the presence of rounded ends, which help to evenly distribute internal pressure and minimize weak points.
Step-by-step explanation:
The identifying characteristic of a pressurized horizontal tank is c. Rounded ends. These rounded ends, also known as 'dish ends' or 'heads', are essential to evenly distribute the pressure inside the tank and reduce the risk of points of weakness where the tank might fail under pressure. Unlike an enclosed dome or white paint, which don't bear a functional role in handling pressure, or external structural reinforcing ribs which are typically found on vertical tanks to combat buckling, rounded ends are inherent to the design of pressurized horizontal tanks. Communal water systems and compressed natural gas (CNG) storage tanks are common examples where you may find such a configuration.