Namespaces in C#.NET: evaluate the statements and choose the correct combination. Statements: 1) Classes must belong to a namespace, whereas structures need not. 2) Every class, struct, enum, delegate, and interface belongs to some namespace (including the global namespace if none is specified). 3) All elements of a namespace must reside in one single file. 4) If no namespace is mentioned, a namespace with the project name is assumed. 5) You must import a namespace with a using directive to use its elements (fully qualified names are not allowed).

Introduction / Context:
This item tests nuanced understanding of how C# organizes types into namespaces, including the special global namespace. It also addresses misconceptions about files and using directives.

Given Data / Assumptions:

• All types exist within a namespace context; if you omit one, the global namespace is used.
• Namespaces span files and assemblies.
• using directives are conveniences, not requirements.

Concept / Approach:
Examine each statement independently and compare it with C# language rules. The global namespace counts as a namespace context even when the code lacks an explicit namespace declaration.

Step-by-Step Solution:

Verification / Alternative check:
Create a class with no namespace and call it via its global name; the code compiles, demonstrating statements 1, 4, and 5 are misconceptions.

Why Other Options Are Wrong:
A and C include false statements; D claims a project-name default (not true); E includes the false requirement for using.

Common Pitfalls:
Equating project name with namespace and assuming files constrain namespace membership.

Final Answer:
2 only