For erythropoiesis to proceed normally, the progenitor cells must receive adequate supplies of which of the following? (1)amino acids (2)calcium (3)iron (4)vitamin B₁₂ (5)vitamin K (6)vitamin A
A) 1, 2, 3, 4, 5, 6 B) 2, 4, 6 C) 1, 3, 5 D) 1, 3, 4 E) 2, 3, 5, 6