Which of the following does not describe hemoglobin?
a.) It binds less tightly to oxygen thanmyoglobin.
b.) It is a multi-subunit protein with four heme groupsfor oxygen binding.
c.) 2,3-bisphosphoglycerate increases its affinity foroxygen.
d.) Maternal hemoglobin has a lower affinity for oxygenthan fetal hemoglobin.
e.) none of the above.