单选题 17. A decrease in face-to-face social contact can precipitate depression. Time spent using the Internet cannot be spent in face-to-face social contact, so psychologists have speculated that sharply increasing Internet use can cause depression. Studies of regular Internet users have found a significantly higher incidence of depression among those who had recently doubled the amount of time they spent using the Internet than among those whose use had not increased. Hence, the psychologists' speculation is correct.
Which of the following is an assumption on which the argument depends? ______

A、 In general, the reason that the people in the studies had doubled their Internet use was not that they had earlier experienced a significant decrease in opportunities for face-to-face social contact.
B、 A sharp decrease in face-to-face social contact is the only change in daily activity that can lead to an increased incidence of depression.
C、 Using the Internet presents no opportunities for people to increase the amount of face-to-face social contact they experienced in their daily lives.
D、 Regular Internet users who are depressed will experience an immediate improvement in mood if they sharply decrease the amount of time they spend on the Internet.
E、 Before they doubled the time they spent on the Internet, the people who did so were already more prone to depression than are regular Internet users in general.

【正确答案】 C

【答案解析】 C：选项取反。使用互联网提供增加面对面社交的机会。再根据文章第一句，面对面社交增加导致抑郁下降。因此该选项取反，上网→面对面社交增加→抑郁下降，削弱原文，正确。
A：选项取反。面对面社交减少→上网时间增加。再根据文章第一句可知，面对面减少→抑郁增加。因此该选项取反后，上网时间增加与抑郁增加产生了关联，加强原文，不选。
B：选项取反。面对面社交的减少不是唯一导致抑郁增加的变化。取反后说明，面对面社交减少依然会导致抑郁增加，加强原文，不选。
D：选项取反。减少上网→心情不会立刻改善。心情不会立刻改善与抑郁上升还是下降无关，不选。
E：该选项本身就说明，这些抑郁的上网者不是因为上网导致抑郁，而是因为本来就容易得抑郁症，削弱原文，不选。