溶菌酶对革兰阴性菌杀菌作用弱，主要是因为
A．无磷壁酸
B．无肽聚糖
C．有外膜保护作用
D．有二氨基庚二酸
E．无脂蛋白
参考答案：C
According to Piaget, thought or thinking has its origin in actions physically performed and then ______. In other words, thought is actions.
芍药汤与白头翁汤两方组成中均含有的药物是（）
A.甘草
B.黄芩
C.黄柏
D.黄连
E.大黄
