Common elements of preventive maintenance include _____.

Preventive maintenance is a proactive approach to maintaining equipment and machinery to ensure their proper functioning and to prevent future breakdowns. The essence of preventive maintenance lies in regular inspections, adjustments, and replacements that help to prolong the life of equipment.

One common element of preventive maintenance is the checking of catenary sag and adjustment. This involves ensuring that overhead lines or cables have the appropriate slack, as improper sag can lead to premature wear or operational issues.

Another important aspect is checking proper alignment, which is crucial for machinery to operate efficiently. Misalignment can cause undue stress on components, increasing the risk of failure and necessitating more frequent repairs.

Additionally, routine checking of all threaded fasteners is integral, as loose fasteners can lead to equipment malfunction or even catastrophic failure. Tightening these fasteners on a regular basis ensures that all equipment remains secure and functions as intended.

Since all these elements contribute to a comprehensive preventive maintenance strategy, selecting the option indicating that all are correct accurately reflects the holistic nature of effective maintenance practices. Each of these tasks plays a vital role in minimizing downtime and extending the life of equipment, making them essential components of a preventive maintenance plan.