GMAT Critical Reasoning (CR) | Re: Until she was given tenure at the college, Susan was considered

Until she was given tenure at the college, Susan was considered an average teacher. It is clear that if her receiving tenure was justified, then Susan was much better than average or very loyal. Soon after she was awarded tenure, however, it was shown that she was not better than average. Thus, one is forced to conclude that Susan must have been very loyal.

Which one of the following states an assumption upon which the argument depends?

(A) Susan being given tenure was justified. (B) Susan was
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