单项选择题
A.flat B.slat C.sweet D.acid
The domestic fresh water pump starters are controlled b...
单项选择题The domestic fresh water pump starters are controlled by pressure switches which operate when the pressure in the tank varies within predetermined limits as water is drawn offThe word “which” means （）.
A.starters B.pressure switches C.pressure D.water
In general, domestic flesh water tank kept under pressu...
单项选择题In general, domestic flesh water tank kept under pressure by an external supply of （）.
A.forced circulating pump B.compressed air C.gravity tank D.bead tank
The abbreviation "TDS" about the potable water probably...
单项选择题The abbreviation "TDS" about the potable water probably means （）.
A.total dissolved solids B.temperature of distillation of sea water C.total dissolved sodium D.total delivery system
