It is unlikely that "C" is load-bearing. Load-bearing walls in the basement level seem to be made of concrete blocks. "C" was probably added later. To be really sure, however, one needs to know how the beams for the upper floor's ceiling are laid out.
No, "C" is not load-bearing. Also, I think the pictures indicate a certain "carelessness," but perhaps you have demolished to be able to see?
What I was wondering about was whether that striped structure could indicate something load-bearing, like the chimney stack in old houses. Based on the drawing, the walls themselves do not appear to be of the load-bearing type.
To be sure, check by sawing by hand. If the saw blade pinches, the beam you are about to cut is load-bearing. Leave the saw in place, set up props and provide support in an appropriate way before continuing to saw.
To be sure, check by sawing by hand. If the saw blade pinches, the beam you are about to cut is load-bearing. Leave the saw in place, set up props and provide support in an appropriate way before continuing to saw.