A Bill of Material (BOM) in MRP is defined as:
a. Bill of Materials organized by major subassemblies or by product options
b. A listing of components, their descriptions, and the quantities of each required to make one unit of a product
c. A number that identifies items at their lowest level at which they occur
d. BOM is not used in MRP

The correct answer is letter "B": A listing of components, their descriptions, and the quantities of each required to make one unit of a product.

Explanation:

A Bill of Material (BOM) in Materials Requirement Planning (MRP) relates the final product with the raw materials, assemblies, parts, and components necessary to manufacture a unit of that good. The BOM is a document that itemizes all the resources necessary to produce a good including at the top the product itself and a listing in hierarchical orders from components to individual materials.  

Creating an accurate BOM helps to have all the material necessary for production available.

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