 Unless something very strange is going on, (B) is an example of a justified belief. DB tells us that (B) is basic if and only if it does not owe its justification to any other beliefs of yours. So if (B) is indeed basic, there might be some item or other to which (B) owes its justification, but that item would not be another belief of yours. We call this kind of basicality “doxastic” because it makes basicality a function of how your doxastic system (your belief system) is structured.