Which type of maintenance involves simple operations and small part replacements without complex assemblies?

The best choice for the type of maintenance that involves simple operations and small part replacements without complex assemblies is preventive maintenance. This kind of maintenance focuses on regular and routine tasks aimed at preventing equipment failures and prolonging service life.

Preventive maintenance often includes tasks like lubrication, adjusting components, and replacing minor parts before they fail. These operations are generally straightforward and do not require significant disassembly or complex assembly procedures. The purpose is to maintain equipment in optimum working condition, thus avoiding more severe issues later on.

In contrast, major repairs typically involve significant assembly or disassembly and are often necessitated by a major failure. Minor repairs, while they might sound similar to preventive maintenance, often deal with unexpected issues that need to be resolved, but they can still involve more than just simple tasks. Modifications generally refer to alterations made to improve performance or capabilities, which can also be more complex than standard maintenance activities.