What component is part of the coupler on a train?

The electric portion of the coupler is essential because it provides the necessary connections for electrical systems between the coupled train cars. This electric connection allows for various functions, such as signaling, lighting, and control systems, to operate seamlessly across the train’s length. Without this component, essential electrical systems would not function correctly, hindering communication and operational efficiency between different train units.

In contrast, other components listed in the options, such as the air brake system, handbrake lever, and main control panel, serve different functions related to train braking and operational control but are not integral parts of the coupler itself. The air brake system is related to the braking mechanism, the handbrake lever is for manual application of brakes, and the main control panel is where the train operator manages controls and gauges. Thus, while they are important for train operations, they do not form part of the coupler's function or structure.