不定项选择题 The value of the Aerodynamic Particle Diameter of a 1μm diameter spherical particle with density 4g/cm³ is ______. Assume that the Cunningham correctionfactor can be neglected。
   A．4μm(g/cm³)^0.5    B．1.0μ_a    C．2.0μ_a    D．4μ_a    E．2.0μm(g/cm³)^0.5