催化剂高温气提时，循环气中硫化氢含量要保持在（）
A、0.05%以上
B、0.1%以上
C、0.15%以上
D、0.2%以上
参考答案：B
My daughter likes to have her photos taken there are many different kinds of
flowers．
A．there
B．in which
C．when
D．where
停炉后18小时内应严密关闭所有的锅炉人孔门、看火孔、打焦孔、检查孔，防止锅炉急骤冷却。
