What is a key feature of the SMFT related to water transport?

The key feature of the SMFT (Self-Contained Mobile Fuel Tank) related to water transport being that it must be transported full or empty reflects critical operational requirements for safety and efficiency in logistics. By ensuring that the tank is either completely full or completely empty during transport, the integrity of the tank is maintained, preventing any issues that might arise from transport with partially filled tanks, such as sloshing, which can impact stability and handling dynamics.

Transporting the SMFT full ensures that it can deliver its intended capacity for water or fuel without introducing complications associated with varying levels of liquid. Conversely, transporting it completely empty avoids unnecessary weight and potential contamination of the contents. This operational guideline is essential for effective management in large-scale combat operations, where logistics, safety, and operational functionality are paramount.

In contrast, the other options do not encapsulate the operational principles that dictate the SMFT's transport protocols, such as purification capabilities, maximum capacity, or power requirements, which are not central to the tank's main transport feature.