A says that polyarchies on the whole are only able to be truly democratic to a limited extent. We have Dahl on the record as agreeing with this around line 55, where he admits the cannot be as democratic as some demand.
C is narrower than A, it is that people living within these polyarchies all have he same access to the sort of things that give political power. Dahl does not think this, in the last paragraph we are told that Dahl actually gave some ground to critics who raised this line of attack.