If vector a, b, c are three non-coplanar vectors and p, q, r are vectors defined by the relations vector p = (b x c)/[abc], q = (c x a)/[abc], r = (a x b)/[abc], then the value of expression (a + b)p + (b + c)q + (c + a).r is equal to
(A) 0
(B) 1
(C) 2
(D) 3