Hardly a week goes by without some advance in technology that would have seemed incredible 50 years ago.
【正确答案】 D
【答案解析】解析：句中词“incredible”表示“难以置信的”。A项表示“难以发明”；B项表示“难以理解”；C项表示“难以想象”；D项表示“难以相信”。D项的词义与原文相符，所以应该选D。