【单选题】压力控制阀中,出口压力保持恒定的阀是( )
【简答题】厂区雨水排除方式 主要有 、 和混合式。
【单选题】在压力控制阀中,出口压力保持恒定的阀是:
【单选题】Climbing is one of _____, I think. [ ]
A.
the most difficult sport
B.
the most difficult sports
【单选题】Climbing is one of ______, I think. [ ]
A.
the most difficult activity
B.
the most difficult activities
C.
most difficult activity
D.
most difficult activities