justify and sufficient assumption are one and the same, justify asks you to strengthen the argument to the point where the conclusion is a necessary condition, so the answer choice you find make the argument 100% true. the answer choice is sufficient in that it makes the arguments conclusion necessary, the answer choice you select should completely validate the argument.
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I think justify questions are PSA questions
justify and sufficient assumption are one and the same, justify asks you to strengthen the argument to the point where the conclusion is a necessary condition, so the answer choice you find make the argument 100% true. the answer choice is sufficient in that it makes the arguments conclusion necessary, the answer choice you select should completely validate the argument.