垄断竞争厂商的平均收益曲线是一条（）
A．平行于横轴的直线
B．向右下方倾斜的线
C．垂直于横轴的线
D．与需求曲线重合的线
参考答案：B, D
Many companies are eager to sign a contract with Zhang Lianying, who has the potential to______ a super star.
A．remain
B．grow
C．make
D．turn
对保护间隙的接地线有什么要求？
