Which of the following is essential for demonstrating the relationship between parts in a drafted assembly?

A bill of materials (BOM) is essential for demonstrating the relationship between parts in a drafted assembly because it provides a structured list detailing all the components, their quantities, and often their part numbers. This document serves as a critical reference that allows one to understand how the individual parts come together to form the complete assembly. A BOM not only outlines the parts but can also indicate the hierarchical structure of the parts, showing how they fit together in the design process, making it crucial for communication among engineers, manufacturers, and assemblers.

While assembly views can visually represent how parts fit together, they do not necessarily provide detailed information about the quantities and relationships in a structured format like a BOM does. Detail drawings focus on specific features of individual parts rather than the relationship between them, and sectioned views offer an internal perspective of components but do not list or explain the relationships amongst multiple parts in an assembly. The BOM consolidates all this in a manageable format, which is why it is considered essential for illustrating part relationships in an assembly context.