Outline the Sequence of the Process That Stimulates the Increase

Outline the sequence of the process that stimulates the increase in the production of red blood cells. (Separate letters by a comma and space as follows: A, B, C, D)
A) Kidneys release erythropoietic factor
B) Increase in red blood cell production
C) Enzyme stimulates red bone marrow
D) Oxygen delivery increased to the tissues
E) Oxygen delivery decreased to the tissues
F) Decrease in red blood cell production