蒽醌用发烟硫酸做磺化剂时常加入硫酸汞其主要作用是（）
A.改变磺酸基的定位
B.抑制砜的生成
C.加快反应速度
D.盐析磺化物
参考答案：A
He was seriously hurt after that accident, but now he was recovered from it. Which of the following can take the place of the underlined word?[ ]
A. taken up
B. taken out
C. picked up
D. picked out
露天安装变压器时，与火灾危险场所的距离不应小于（）。
A.10m
B.15m
C.20m
D.25m
