根据所学课文内容填空

     At first my new  1   were difficult to tolerate. The air seemed thin, as  2   its combination of gases

had little oxygen left.    3   by a lack of fresh air, my head ached. Wang ping handed a mask to me

and I felt better in   4   time. Soon I was   5   on my feet again and following him to collect a hovering

carriage driven by computer. Wang Ping   6   my safety belt and showed me how to use it. Soon I

could fly as fast as him. However, I lost   7   of him when we reached   8   looked like a lager market

because of too many carriage flying in all directions.

防毒面具应按照正常值班情况下的最多人数配置，无人值班变电占应按500kV变电站不应少于4个，220kV及以下变电站（）来配置。

A.不应少于1个

B.不应少于2个

C.不应少于3个

D.不应少于4个