——Your mother's never seen a 3D film at the cinema, has she?—— ____, but only once.
A:Yes, she has
B:No, she hasn't
C:Yes, she is
D:No, she isn't
明人朱载堉在《十不足》歌写道:“逐日奔忙只为饥,才得有食又思衣。置下绫罗身上穿,抬头又嫌房屋低。……若非此人大限到,上到天上还嫌低。”这说明( )
牙龈经常出血的人,体内可能缺乏的维生素是( )