You are designing a class library by using the .NET Framework 3.5 and Microsoft SQL Server 2008.
The class library will be used by several .NET applications. The class library will contain a utility class that executes advanced mathematical operations.
You need to design the utility class to meet the following requirements:
– It can be accessed only by other classes in the same .NET assembly.
– It can be instantiated only once.
What should you do?

A.
Create a public class along with an internal constructor.

B.
Create an internal class along with an internal constructor.

C.
Create a public class along with a private constructor. Expose a public static method that returns an instance of the class.

D.
Create an internal class along with a private constructor. Expose an internal static method that returns an instance of the class.