含亚铁盐地下水抽出地面后呈现（）。
A.棕色或棕黄色
B.绿色或黄绿色
C.黄褐色
D.黑色
E.蓝色
参考答案：C
Not only his parents but also his elder brother _____ to the Summer Palace. They haven’t been back yet.[ ]
A. have been
B. have gone
C.has gone
D. has been
极值误差
