Ms Black is considered a________lady by her neighbors, for she often helps the poor old man next door.  [      ]

A. generous  

B. hopeful

C. mean  

D. selfish

220kV开关气体压力额定值为0.5MPa，气体压力低于报警值0.45MPa时报警；气体压力低于闭锁值0.4MPa压力时，闭锁压力继电器动作切断合闸、分闸操作控制回路，断路器不能进行（）和（）操作。