Hierarchical dependency resolutions in inheritance c#

To maintain the separation of concern, I am trying to create the layered project architecture. lets consider below example.

• ProjectA is class library and has

  • interface IntefaceA
  • Abstract Class ClassA implements InterfaceA

• ProjectB is class library and reference ProjectA and has

  • Abstract Class ClassB inherit ClassA ( PrjectA reference added in ProjectB )
• ProjectC has
  • Class ClassC which inherited from ClassB so added ProjectB as reference in ProjectC

Now issue is, in ProjectC I am getting error The type ClassA is defined in an assembly that is not referenced

Questions is

1. Why ProjectC need ProjectA reference
2. Do I need to add all the referenced project all way to the hierarchical chain
3. How can I achieve separated design while reducing the dependency