The pavements are designed to provide easy access for the blind to _______conveniently, which is          bound to_______ active effects on people’s opinion on the government’s performance.

A．walk ; produce

B．walking ; producing

C．walk ; producing

D．walking ; produce

热力膨胀阀的调节作用是( )。

A．用流量的变化调节蒸发温度
B．用流量的变化调节蒸发皿出口制冷剂蒸气的过热度
C．用压力的变化调节蒸发皿出口制冷剂蒸气的过热度
D．用压力的变化调节蒸发温度