Which of the following is a core aspect of alteration standards?

Modifications to plumbing, heating, or electrical systems are a core aspect of alteration standards because these systems are critical to the safety, functionality, and habitability of a manufactured home. Alteration standards are designed to ensure that any changes made do not compromise the integrity of these essential systems. Such modifications must comply with local codes and regulations to avoid safety hazards and maintain performance standards.

Energy efficiency ratings, while important, focus more on the overall performance of a home rather than specific alterations. Landscaping changes are often related to aesthetics rather than structural integrity or safety. Approval of architectural styles, while relevant in terms of design compliance, does not pertain directly to the physical alterations of the home's essential systems. Thus, the focus on plumbing, heating, and electrical systems underlines the importance of safety and compliance in residential housing standards.