【单选题】

Although scientists have long ------- the human appendix as ------- organ, there is a growing body of evidence indicating that the appendix does in fact have a significant function as a part of the body's immune system.
A．(A) overestimated ... a minor

B．(B) discounted ... a vestigial
C．(C) valued ... a major
D．(D) ignored ... a pivotal
E．(E) studied ... an inaccessible