Which is a characteristic of a compressed gas tube trailer?

The characteristic of a compressed gas tube trailer includes that the manifold or valve control box is enclosed at the rear. This design is crucial for safety and functionality, as it helps protect the control apparatus from environmental exposure and potential damage during transport. The enclosure minimizes the risk of accidents associated with external elements and provides a secure and organized location for the trailer's operational components.

In contrast, the other options provide characteristics that do not accurately describe a compressed gas tube trailer. For example, temporary markings for material or ownership are not a standard feature, as trailers typically display permanent identification and hazard markings for safety and regulatory compliance. Additionally, while some trailers may carry liquefied gases, this does not apply exclusively to compressed gas tube trailers, which are designed specifically for the safe transport of compressed gases in tube form. Furthermore, carrying only non-flammable gases is too restrictive, as tube trailers can transport a variety of gases, including flammable and corrosive ones, as long as they are properly classified and handled.