Using a namespace contained in a library: choose the correct sequence to make its elements available in your project.

Introduction / Context:
To consume types from an external library, you must reference the assembly and optionally add using directives. This question checks the exact order of operations.

Given Data / Assumptions:

• Types live in assemblies; namespaces are logical groupings within those assemblies.
• Referencing assemblies differs from adding using directives.

Concept / Approach:
Reference resolves the binary dependency; using resolves name lookup convenience within source code. Without the reference, the compiler/linker cannot locate the types, regardless of usings.

Step-by-Step Solution:

Verification / Alternative check:
Try to compile with only using and no reference; the build fails because the type is unresolved.

Why Other Options Are Wrong:
A confuses namespaces with assemblies; C misses the required reference; D is not sufficient; E is unnecessary for most scenarios and does not by itself wire references.

Common Pitfalls:
Believing using imports binaries, or thinking copying the DLL beside the EXE is enough without adding a reference.

Final Answer:
Add a reference to the assembly that contains the namespace. Import the namespace with a using directive. Use its elements.