单项选择题
A.1/4-1/3B.1/4-1/2C.1/3-1/2D.1-1/4
A.0.2-0.45MPaB.0.2-0.55MPaC.0.2-0.65MPaD.0.45-0.65MPa
A.300-350B.280-300C.400-450D.380-400