【单选题】变量泵节流调速系统中溢流阀的作用为( )
【单选题】What do we know about the girl?
A.
She is new to the school.
B.
She writes for school newspaper.
C.
She seldom asks questions in class.
【判断题】频分复用是一种按频率来划分信道的复用方法。
【单选题】She'supstairs______ letters.
【多选题】能调节系统压力的大小,且能维持系统压力近于恒定的压力阀称为溢流阀。其功用是()。