Answer: (ii) To visualize and document software architecture

UML (Unified Modeling Language) is a standardized visual modeling language used to visualize, specify, construct, and document the artifacts of a software system — architecture, design, and behaviour — through diagrams (class, use-case, sequence, deployment, etc.).

Why the others are wrong:

• (i) To write executable code — UML is a modeling language; code generation is possible but not its main purpose.
• (iii) To enforce coding standards — coding standards are separate; UML specifies design, not coding rules.
• (iv) To test software functionality — testing uses the design but UML itself is not a testing tool.

So the main purpose of UML is to visualize and document software architecture — option (ii).