GMAT Critical Reasoning (CR) | Re: The Fieldpark nuclear power plant, cited three years ago by a

Dear Mike,

While I was reviewing this question in Magoosh, there was something interesting about choice B. It is stated that B is weakener. I heard Chris in his video says the same. However, I do not understand how B can weaken the argument. I hope you can clarify this point.

Thanks for your help.