（）中CO含量相对最高。
A.高炉煤气
B.焦炉煤气
C.转炉煤气
参考答案：C
-Jack has made great progress recently.
-________, and ________. [ ]
A. So he has, so you have
B. So he has, so have you
C. So has he, so have you
D. So has he, so you have
