Monthly inspections of the stacker should cover which of the following?

Monthly inspections of the stacker should comprehensively evaluate critical safety and operational components, which is why the correct choice encompasses brakes, interservice, and various instruments. These elements are essential for the safe and effective operation of the stacker.

Brakes are a fundamental aspect of any lifting equipment, as they ensure the stacker can stop safely under load. Inspecting the brakes for wear and functionality helps prevent accidents and equipment failures. The term "interservice" likely refers to the operational status of various components and systems that support the effective functioning of the stacker, ensuring that everything operates harmoniously.

Moreover, various instruments would include essential gauges and indicators that provide feedback about the stacker's performance and operational condition. Regular checks on these instruments help operators stay aware of any potential issues before they escalate.

In contrast, while exterior condition and paint, wheel alignment and tire pressure, and seat adjustments certainly contribute to the overall maintenance and usability of the stacker, they do not address the critical safety functionalities as directly as the components mentioned in the correct choice. These aspects, while important for the maintenance of the equipment's aesthetic and comfort, are of secondary priority compared to ensuring that the essential operational safety features are in optimal working condition.