What is the necessary condition for slack adjusters during inspection?

For slack adjusters during an inspection, the necessary condition is that there should be no loose or missing bolts. Proper attachment of slack adjusters is crucial, as they play an essential role in the effective operation of the brake system. If bolts are loose or missing, it can result in improper functioning, leading to braking issues, which can compromise safety. Ensuring that all components are securely fastened helps maintain the integrity of the brake system and prevents potential failures during operation.

The other options refer to different aspects that may not meet the critical safety requirements for slack adjusters. For example, excessively lubricated mechanisms can attract dirt and debris, leading to maintenance issues. Adjustability without resistance is not a standard requirement, as some resistance may indicate proper function. Lastly, while visible wear indicators can provide useful information, they are not fundamental to the immediate functional integrity of the slack adjuster itself during an inspection.