Namespaces in C#.NET: which statement is correct regarding nesting and imports?

Introduction / Context:
Nesting namespaces is a standard organizational pattern in C#.NET, especially in large libraries. This question checks your understanding of nested namespace support and importing behavior.

Given Data / Assumptions:

• Large frameworks often have multi-level namespaces (e.g., System.Drawing.Drawing2D).
• Using directives are optional when fully qualifying type names.

Concept / Approach:
C# supports nested namespaces, and files can contain multiple namespace declarations. Importing a parent does not implicitly import children; each must be imported or fully qualified as needed.

Step-by-Step Solution:

Verification / Alternative check:
Try referencing types in System.IO without using System.IO; you must either add that using or fully qualify type names.

Why Other Options Are Wrong:
They contradict language rules about nesting and imports or overstate requirements.

Common Pitfalls:
Assuming a parent using brings in all descendants automatically.

Final Answer:
Nested namespaces are allowed and commonly used to organize large codebases.