炭疽的检疫多采用()实验。
A.HA
B.中和实验
C.变态反应
D.环状沉淀反应
参考答案:D
The problem _______ at tomorrow's meeting is a very difficult one. [ ]
A. being discussed
B. discussed
C. to be discussed
D. to discuss
污水处理站的通信管道为()镀锌钢管组成。
A.DN100
B.DN200
C.DN300
D.DN400