【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