What is one difference between the erythrocytes of mammals and other vertebrates?

A) Mammalian erythrocytes lack nuclei.
B) Mammalian erythrocytes respond to changes in water concentration.
C) Mammalian erythrocytes are oval with swollen centers.
D) Other vertebrates do not have erythrocytes.
E) Other vertebrates use a respiratory pigment other than hemoglobin.