Which of the following cell types is an immature red blood cell?

Plasma is ____ while formed elements are ____. a. a blood gas; blood clots
b. the liquid portion of blood; the cells
c. lacking in protein; regulators of blood osmolality
d. the cellular portion of blood; acellular components
e. mostly protein; the matrix

Which of the following cell types is an immature red blood cell?
a. erythrocyteb. reticulocytec. thrombocyte
d. monocyte
e. leukocyte