I see it this way:
If a> 0, then the question is: a=b-c?
If a<0, then the question is: a=c-b?
not sufficient, we need to know whether a>0 to answer that question.
a>0, but we don't know anything about the relationship between a,b and c
Together, A<0. Therefore the question is: Is a=c-b? And (1) does not tell us that.
My answer is therefore E: Problem the OA is C.
Either I am wrong or the OA is wrong. Would anyone know?