**Core Concept**
In the process of erythropoiesis, the development of red blood cells (RBCs) from hematopoietic stem cells, the first cell type that emerges is crucial for the subsequent differentiation steps. This initial cell type is characterized by its unique morphology and function.

**Why the Correct Answer is Right**
The first cell in RBC development is the **proerythroblast**, which is a large, immature cell that contains a large nucleus and a small amount of cytoplasm. This cell type is characterized by the presence of a prominent nucleolus and a small amount of hemoglobin. The proerythroblast is the first cell in the RBC lineage to undergo significant changes in its morphology and function, marking the beginning of the erythropoietic process.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the proerythroblast is the first cell in RBC development, not the **basophilic erythroblast**, which is a later cell type in the RBC lineage that is characterized by its dense, basophilic cytoplasm.
**Option B:** This option is incorrect because the **normoblast** is a later cell type in the RBC lineage that is characterized by its larger size and more mature morphology.
**Option C:** This option is incorrect because the **megaloblast** is a cell type associated with megaloblastic anemia, a disorder characterized by the production of large, abnormal RBCs.

**Clinical Pearl / High-Yield Fact**
The proerythroblast is the cell type that is most susceptible to the effects of anemia-inducing substances, such as lead or other heavy metals, which can interfere with the normal development of RBCs.

**Correct Answer: C. Megaloblast. Proerythroblast.**