I think B is a valid reason, and possibly the true one. C may be true, but I think the belief "I'm inadequate" could lead to anticipating failure at some task or goal, and the belief "I'm adequate" could lead to anticipating success. Also, since the patient already believes e is inadequate, the motivated skepticism is in the opposite direction from es current belief--essentially compensating for an existing bias. Playing biases off each other isn't the best way to get the truth, but it is sometimes the best way available.

Oh, btw, the formatting on the links didn't work quite right.