联合用药种类越多，不良反应发生率也越低.
参考答案：错
Experienced as she is, the teacher is still thinking of new ideas about how the new textbooks should be ______ .
A．conducted
B．made
C．sent
D．carried
在垄断者的最优产出水平（）
A.MR=MC
B.P=MC
C.P=平均成本的最小值
D.P最大
