某集气瓶里盛有空气，欲除去其中的氧气而得到较纯净的氮气时，最好采用的物质是 A．蜡烛 B．木炭 C．红磷 D．硫粉
After giving a talk at a high school, I was asked to pay a visit to a special student. An illness had kept the boy home, but he had expressed an interest in meeting me. I was told it would mean a
北宋前期统治者认为“富室连田阡陌，为国守财尔！缓急盗贼窃发，边境扰动，兼并之财，乐于输纳，皆我之物。”这表明北宋政府 A、大力抑制土地兼
At first Bob was puzzled by Virginia s waving, but then it _____ his mind that she was trying to tell him something. A. crossed B. passed C. occurred D. opened
鸟类的性别决定为ZW型。某种鸟类的眼色受两对独立遗传的基团(A、a和B、b)控制。甲、乙是两个纯合品种，均为红色眼。根据下列杂交结果，推测杂交1
一对夫妇生出的儿子体内性染色体为 A．XXB．XYC．YY D．不确定
