Which of the Following Occurs in Hemoglobin Upon Oxygen Binding

Which of the following occurs in hemoglobin upon oxygen binding?

A) the heme Fe²⁺ is pulled out of the plane of the heme group
B) the His coordinated to the heme Fe²⁺ is pushed away from the heme group
C) the central cavity between the four subunits is decreased in size
D) hemoglobin changes from the R state to the T state
E) all of the above occur