单选题 You are exposed to obtrusive ads that ______ seemingly from nowhere even when you are disconnected from the Net，and your personal information gathered and sent off without you being aware of it．
A．size up B．dwindle away C．conjure up D．pop up

【正确答案】 D
【答案解析】[解析] size up评估……的大小；dwindle away减少，缩小；conjure up用魔法召；pop up突然出现。