单项选择题
A.People can know the types of fluids in pipes by feeling with hands
B.There are series of rings painted in the pipes to show various fluids
C.Engineers should wear cards standing for ranks
D.Engineer knows his own code very well
单项选择题 Disastrous explosions have been caused by accumulations of oil or oil vapour in air lines not drainedAccording to the above sentence, which of the following statements is true?（）
单项选择题 In usual marine applications, bellows joints are designed and fitted to accommodate straight line axial movement only and the associated piping requires adequate anchors and guides to prevent misalignmentAccording to the above sentence, which of the following statements is true?（）
单项选择题 Maximum and minimum working temperatures must be considered when choosing the joint, which must be so installed that it is neither over-compressed nor over-extendedThe bold and italic word "which "probably means （）.