单项选择题
A.in the store room
B.in the cylinder
C.in the scavenge air box
D.in the water box
单项选择题 Water level controllers of the boiler must be kept operable to protect external steam-using plant from water “（）” danger.
单项选择题 The （） of the gravity disc is too big It causes oil to flow through the water outletWe changed the disc and no oil is found in the water outlet.
单项选择题 The designed （） is 20 tons per day, but the fresh water generator can only distil 15 tons at present.