条件型结论：结论带条件（即为充分必要）。ASSUMPTION的方法排除充分条件出现，必要条件不出现的情况。或充分条件一定能推出必要条件，或排除充分条件推不出必要条件的可能。
50. Although computers can enhance people’s ability to communicate, computer games are a cause of underdeveloped communication skills in children. After-school hours spent playing computer games are hours not spent talking with people. Therefore, children who spend all their spare time playing these games have less experience in interpersonal communication than other children have.
正确答案是Children who do not spend all of their after school hours playing computer games spend at least some of that time talking with other people.
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