题目

 This cake is very sweet. You ____ a lot of sugar in it.      A. should put      B. could have put      C. might put    D. must have put 答案：D细胞膜上与细胞的识别、信息传递有密切关系的化学物质是 （ ）A．糖蛋白 B．磷脂 C．脂肪 D．蛋白质