最常用的市场调研方法是（）。
A．观察法
B．访问法
C．实验法
D．统计分析法
参考答案：B
—You speak English very well.
—________.[ ]
A. No, not good
B. Thanks
C. Not at all
D. You're welcome
The math problem is so hard. I really don't know_____. [ ]
A. how to do it
B. how to do
C. what to do it
