A hematopoietic stem cell is defined as A．a cell with extensive self-renewal and proliferative potential B．a cell only to produce daughter cells with identical characteristics C．a cell with the capacity to differentiate into the progenitors of all the blood cell lineages D．a cell With the capacity to produce some hematopoietic growth factors such as SCF，GM-CSFs，et．a1． E．a cell with the capacity to express some specific surface antigens such as CD34