During a pre-trip inspection, which of the following is a necessary component of the lighting indicators?

During a pre-trip inspection, ensuring that the left and right turn signals are functioning properly is essential for safety and compliance. The turn signals are critical indicators of a driver's intention to change direction or lane, which helps prevent accidents and miscommunications with other road users. The presence and proper operation of these indicators allows the driver to alert others when making turns or lane changes, thus enhancing safety on the road.

While other components like headlight adjustment, brake light warnings, and interior dome lights are important in their own right, the left and right turn signals have a direct impact on the vehicle's communication with other drivers. They are part of the legal requirements for operating a commercial vehicle, ensuring the driver can signal their maneuvers clearly. Not having functioning turn signals could lead to confusion on the road and result in dangerous situations. Hence, their operational status is a crucial aspect during the pre-trip inspection.