B must be defined before you use it in the declaration of A::myData.
I think all you need to do is put the class definition in front of the declaration of the variable. The compiler has no idea what is inside class B, only that it exists, until it encounters the actual definition of the class.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.