营养不良性口角炎最常见的病因是缺乏（）
A.维生素C
B.维生素B1
C.核黄素
D.维生素E
E.微量元素铁
参考答案：C
气管异物易坠入哪侧主支气管，为什么?
When______where he was born,John said he was a New Yorker.
A,asking B,being asked C,asked D,was asked
