Why should you pull a dolly out from under a trailer before disconnecting?

The correct choice is based on the understanding of the mechanics involved when disconnecting a dolly from a trailer. Pulling the dolly out from under the trailer before disconnecting is essential because if it is not done properly, the tow bar of the dolly can indeed fly up unexpectedly. This could pose a significant safety risk to anyone in the vicinity, potentially causing injury.

The movement of the dolly's tow bar is related to the positioning and tension in the connection between the dolly and the trailer. If the dolly is not removed correctly, the sudden release can lead to a rapid movement of the components, which could result in a dangerous scenario.

This highlights the importance of following safety protocols and procedures when working with heavy equipment. Ensuring that all components are safely managed will help minimize risks during the disconnecting process.