**Core Concept**
The question is testing the student's knowledge of cluster of differentiation (CD) markers, specifically those associated with the myeloid series of cells. CD markers are proteins expressed on the surface of immune cells, and they play a crucial role in identifying and characterizing various cell types.

**Why the Correct Answer is Right**
The correct answer is a specific CD marker that is highly expressed on cells of the myeloid lineage, including monocytes, macrophages, neutrophils, and eosinophils. This CD marker is a transmembrane glycoprotein that serves as a receptor for various ligands, including complement components and cytokines. Expression of this CD marker is a hallmark of myeloid cells and is used as a diagnostic marker in immunohistochemistry and flow cytometry.

**Why Each Wrong Option is Incorrect**
* **Option A:** This CD marker is not specific to the myeloid series and is also expressed on B cells and other lymphoid cells.
* **Option B:** This CD marker is associated with T cells and is not a marker of myeloid cells.
* **Option C:** This CD marker is expressed on platelets and megakaryocytes, but not on myeloid cells.

**Clinical Pearl / High-Yield Fact**
A key clinical application of CD markers is in the diagnosis of acute leukemia, where specific CD markers can help identify the lineage and maturation stage of leukemic cells.

**Correct Answer:** C. CD61.