A. Create a class to store DLL functions. Create prototype
methods by using the managed code.
B. Use COM to register the assembly. Reference the managed
code from COM.
C. Export a type library for the managed code.
D. Import a type library as an assembly. Create instances of
COM object.

Answer: A

Explanation: It is good practice to wrap the messy P-Invoke
code with a .net class.
The main benefit is to keep the client code tidy as the
messy and cryptic code will be hidden away. Also better for
maintenance e.g dll name or version changes.
The question explicitly says the unmanaged code should be
called with platform invoke services. Importing\exporting a
type library is relevant for interoperation with COM.