请教LSAT一题？

bigmouse

The dean of computing must be respected by the academic staff and be competent to oversee the use of computers on campus. The only deans whom academics respect are those who hold doctoral degrees, and only someone who really knows about computers can competently oversee the use of computers on campus.
Furthermore, the board of trustees has decided that the dean of computing must be selected from among this university’s staff. Therefore, the dean of computing must be a professor from this university’s computer science department.
14. Which one of the following statements, if true, would weaken the argument?
(A) There are members of this university’s staff who hold doctoral degrees and who are not professors but who really know about computers.
(B) There are members of this university’s philosophy department who do not hold doctoral degrees but who really know about computers.
(C) Computer science professors who hold doctoral degrees but who are not members of this university’s staff have applied for the position of dean of computing.
(D) Several members of the board of trustees of this university do not hold doctoral degrees.
(E) Some members of the computer science department at this university are not respected by academics in other departments.
answer:A my choice:B
我的思路：该题应该是一个类比推理，A-->B，解题思路应该采用“断桥”方法（为狒狒作广告），我觉得B也是一个很好的断桥啊，为什么不行？