《政府采购法》规定，（）是投标人投诉的前置条件。
A．协商
B．质疑
C．仲裁
D．复议
参考答案：B
计算397×78时，可以估计到积是一个______位数．
So difficult _____ it to live in an English-speaking country that I determined to learn English well. [ ]
A. I did feel
B. did I feel
C. I have felt
D. have I felt
