单项选择题
A.Spring-centered valve
B.Unloading valve
C.Three-position valve
D.Two-position valve
单项选择题 Which of the listed refrigeration system components keeps the refrigerant circulating through the system?（）
单项选择题 Which of the listed components is considered to separate the high pressure side of a refrigeration cycle from the low pressure side of the cycle?（）
单项选择题 A compound gage is used to measure （）.