压缩机防喘振调节阀的作用形式应怎样选择？
参考答案：
应选择气关式调节阀。
下列物质中，属于电解质的是（ ）
A．铜丝
B．乙醇
C．NaCl溶液
D．MgCl2固体
The news that the students would put off the outing until the next week was ________ yesterday.[ ]
A. confirmed
B. impressed
C. observed
D. delivered
