Object-Oriented Analysis (OOA) is most commonly structured as a five-step process. This approach provides a systematic way to analyze a problem domain and define a system in terms of objects. The five fundamental steps are:

1. Identify Classes: Determine the key objects or concepts in the problem domain.

2. Identify Attributes: Define the data or state for each class.

3. Identify Operations: Define the behavior or methods for each class.

4. Identify Relationships: Establish the connections between classes, such as association, aggregation, and inheritance.

5. Model the System: Create diagrams (like UML Class Diagrams) to represent the static structure and dynamic interactions of the objects.

This five-step framework is a widely taught and practiced standard in software engineering.

A. Three: This number is too simplistic, often failing to separate the distinct and crucial analysis activities of defining attributes, operations, and relationships.

B. Four: While some specific methodologies might propose four steps, the five-step model is more comprehensive and is the most widely recognized standard in academic and practical contexts.

D. Six: A six-step process typically includes activities like requirements elicitation or model review, which are part of the broader software lifecycle rather than the core OOA process itself.

1. Coad, P., & Yourdon, E. (1991). Object-Oriented Analysis (2nd ed.). Prentice Hall. In Chapter 1, "Object-Oriented Analysis," the authors introduce and detail their influential five-step OOA model: Identifying objects, identifying structures, identifying subjects, defining attributes, and defining services.

2. Pressman, R. S., & Maxim, B. R. (2015). Software Engineering: A Practitioner's Approach (8th ed.). McGraw-Hill Education. Chapter 8, "Requirements Modeling: Class-Based Methods," describes the activities for creating a class-based model, which align with the five core steps, including identifying analysis classes, specifying attributes, defining operations, and modeling associations and dependencies.

3. Dennis, A., Wixom, B. H., & Tegarden, D. (2015). Systems Analysis and Design: An Object-Oriented Approach with UML (5th ed.). Wiley. Chapter 5, "Structural Modeling," outlines the process of creating class diagrams by identifying classes, attributes, operations, and relationships, reflecting the core five activities of OOA.