The passage tells us that, if Hastings' dismissal was justified, then he was either incompetent or disloyal.
J --> I or D
Not I AND Not D --> Not J
The passage then concludes that, because it was proven that Hastings had never been incompetent, he must have been disloyal.
Why must Hastings have been disloyal? The only reason this must be true is if the sufficient condition was met i.e if Hastings' dismissal was justified. However, the passage doesn't tell us whether Hastings' dismissal was justified or not.
Therefore, the conclusion can only be properly drawn if we assume that Hastings' dismissal was justified, as is restated by answer choice (A).
Answer choice (B) is incorrect because it is irrelevant. The passage does not mention rank and it is neither a sufficient nor a necessary condition which would impact the passage's conclusion.
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