如果竞争市场的价格超过（），追求利润最大化的厂商将进入。
A.最 * * 均成本
B.边际收益
C.最 * * 均可变成本
D.平均收益
参考答案：A
snacks and drinks, but they also brought cards for entertainment when they had a picnic in the forest.
A．Not only they brought
B．Not only did they bring
C．Not only brought they
D．Not only they did bring
诊断气管异物最主要依据是（）
A.异物吸入史
B.咳嗽
C.呼吸困难
D.听诊肺呼吸音减弱
E.X线肺部阴影
