单项选择题
A.high temperature distillate can be re- circulated to induce additional flashing
B.scale formation is not a severe problem
C.cold shocking is more effective in removing scale
D.water purity is greatly increased at high capacity
单项选择题 A liquid indicator sight glass is useful in determining whether or not a refrigeration system is sufficiently chargedIt is generally located in the（）.
单项选择题 Compared to a constant pitch propeller, a controllable pitch propeller（）.
单项选择题 Compared to a constant pitch propeller, a controllable pitch propeller（）.