@smilde11, the reason why (B) is the answer is that it doesn't modify the argument at all, whereas the others weaken it.
We can assume from the passage that the witness had stated that Congleton wanted to see the project fail, and the lawyer in the question is trying to undermine that conclusion by pointing out that the best people possible were assigned to the project. Whether or not the project could fail without Congleton's intention to undermine it is irrelevant to this argument as the lawyer is only trying to weaken the conclusion that Congleton wanted to see the project fail.
