Pipe B is in the wall. A lav that wet vents the toilet.
Pipe A is 13" in front of the framed wall. This is for a standard 12" rough toilet.
Pipe C needs to be in a wall and it's for the tub drain and vent. This vent will either go through the roof, or tie in at ceiling level and revent to the toilet/Lav vent.
The tub should drain on the inside wall, not the outside wall in a perfect world.
We measure by interior dimension.
It looks like you have 3" and 2" pipe there.