自动控制管道水击超前控制的前提是()质量必须良好。
A.设备
B.阀门
C.通信
D.仪器
参考答案:C
By the time Jack returned home from America, his son __________ from college.
A.graduate
B.has graduated
C.had graduated
D.had been graduated
网关默认SSID为()。