In C sharp and Visual Basic on the .NET platform, how can you prevent a class from being inherited or overridden further so that it cannot act as a base class?

Introduction / Context:
Sometimes a class is designed to represent a complete, final implementation that should not be extended. Allowing further inheritance from such a class could break assumptions, weaken security, or complicate maintenance. The .NET languages C sharp and Visual Basic provide specific keywords to mark classes as final, which prevents them from serving as base classes. This question asks how to express that intention in both languages.

Given Data / Assumptions:

• We are working with C sharp and Visual Basic, which both target the common language runtime.
• We want to mark an entire class so that no new derived classes can inherit from it.
• We are not only preventing override of individual methods but blocking inheritance of the class itself.
• The question asks for the correct keywords or modifiers used to achieve this behavior.

Concept / Approach:
In C sharp, the sealed keyword is used on class declarations to indicate that the class cannot be inherited. For example, sealed class Logger declares a Logger class that cannot act as a base class. In Visual Basic, the equivalent keyword is NotInheritable, placed before the class declaration, as in NotInheritable Class Logger. Marking a class as sealed or NotInheritable instructs the runtime and compiler to reject attempts to derive new types from that class. This is different from abstract or MustInherit classes, which are designed for inheritance and often cannot be instantiated directly.

Step-by-Step Solution:
Step 1: Recall that sealed in C sharp means the class is closed for inheritance and cannot be extended. Step 2: Remember that NotInheritable in Visual Basic has the same effect, marking the class as final. Step 3: Distinguish this from abstract or MustInherit, which encourage inheritance instead of preventing it. Step 4: Choose the option that correctly pairs sealed in C sharp with NotInheritable in Visual Basic and states that the class cannot be used as a base class.

Verification / Alternative check:
If you write sealed class A in C sharp and then attempt class B : A, the compiler reports an error that A is sealed and cannot be inherited. Similarly, in Visual Basic, declaring NotInheritable Class A and then Class B Inherits A triggers a compilation error. These experiments confirm that sealed and NotInheritable are the appropriate modifiers for preventing inheritance of a class, consistent with official documentation for both languages.

Why Other Options Are Wrong:
Option B is wrong because abstract and MustInherit classes are intended to be base classes and often cannot be instantiated themselves. Option C misuses static and Shared, which relate to how members are accessed, not to inheritance rules. Option D is incorrect because omitting an access modifier only affects visibility scope, not inheritance permissions. Option E is wrong because making methods public does not prevent inheritance; it simply allows broader access to those methods.

Common Pitfalls:
Developers sometimes confuse sealed classes with sealed methods. In C sharp, you can seal a method in a derived class to prevent further overrides, but sealing the class itself blocks all inheritance. Another pitfall is overusing sealed everywhere, which can make frameworks rigid and hard to extend. Good design uses sealed or NotInheritable when you truly want to lock down behavior and leave other classes open to extension when future customization is likely. Understanding when and how to mark classes as final helps you balance flexibility with safety and maintainability.

Final Answer:
By declaring the class as sealed in C sharp and NotInheritable in Visual Basic so that it cannot be used as a base class