单项选择题
A.60° B.120° C.90° D.45°
A.192kPa B.292kPa C.392kPa D.492kPa
A.0.142L/s B.0.192L/s C.0.242L/s D.0.292L/s
A.4% B.5% C.6% D.3%
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