sonali, the question was about preventing bedsores ie it assumes there's no bedsores present to start with.
This is why I spoke of vulnerable areas rather than the sores themselves. Reducing the pressure on the sores in the context of the question doesn't come into it as the question doesn't say that sores are present.
Incidentally, this is not nit-picking. The point is that this looks like a typical exam question and you'd get no marks if you talk about reducing pressure on sores that the question doesn't say are present. Until the skin starts to become ulcerated, there's no pain anyway.