The Correct Way To Implement A Write Only Property Add In A #475

The correct way to implement a write only property add in a math class?

This multiple choice question (MCQ) is related to the book/course gs gs108 CSharp. It can also be found in gs gs108 Indexers and Exception Handling - Properties and its Applications - Quiz No.1.

 class math { public int add { set { add = value; } } } 

 class math { int ad; public int add { set { ad = value; } } } 

 class math { int ad; public int add { get { return ad; } set { ad = value; } } }