单项选择题
A.a manual closed loop
B.a manual opened loop
C.an automatic closed loop
D.an automatic opened loop
单项选择题 Bourdon Tube is probably the most commonly used （） measuring instrument.
单项选择题 Movement of the diaphragm or bellows is （） by a linkage to a needle or pointer display to indicate the differential pressure between two sides of the diaphragm or bellows.
单项选择题 When two different metals are joined to form a closed circuit and exposed to different temperatures at their junctions （） which can be used to measure temperature.