Up to now，the program________thousands of children who would otherwise have died.

A．would save

B．saves

C．had saved

D．has saved

感温式火灾探测器据其感热效果和结构型式，可分为定温式、差温式和差定温组合式三类。其中定温火灾探测器的特点是( )。

A．保养维修复杂、响应过程短、可靠性和稳定性好
B．可靠性和稳定性较好、保养维修简单、灵敏度高
C．可靠性和稳定性较好、响应过程长、灵敏度低
D．稳定性差、响应过程长、灵敏度低