以下哪个选项不是提升质量度指标（）
A.提高CTR
B.优化创意
C.内容的相关性
D.提升账户消费
参考答案：D
电梯驱动主机旋转部件的上方应有不小于（）m的垂直净空距离。
A.0.10
B.0.30
C.0.50
D.0.70
I know Mr. Brown；we ＿＿ to each other at an international conference.
A．are introduced
B．have been introduced
C．were introduced
D．had been introduced
