单项选择题
Shims of different thicknesses are inserted between the shells to enable adjustment of （）.
A.the bearing clearances B.the bearing thickness C.the bearing strength D.the bridge hardness
单项选择题 Sediment collects in a tubular purifier （）.
单项选择题 Sea water is not used directly as a coolant because of （）.
单项选择题 Sea water is not directly used as a coolant for engines because of its （）.
