4.In 1928, English microbiologist Frederic Griffith demonstrated that DNA is the genetic material to determine the virulence of bacteria cells； what observations helped this conclusion? (A)' The heat-killed pathogenic bacteria + live non-pathogenic bacteria → pathogenic. (B) The heat-killed non-pathogenic bacteria+ live pathogenic bacteria → pathogenic. (C) The transformation of bacteria was carried by a heat-stable genetic material. (D) Pathogenicity reffects the action of the non-capsule gene. (E) Non-pathogenic bacteria could uptake the capsule gene from the bead pathogenic bacteria.