**Core Concept**
The question is testing the ability to identify a marker specific for the myeloid lineage. Myeloid lineage refers to the hematopoietic cells that give rise to various types of blood cells, including granulocytes, monocytes, and platelets. These cells originate from the myeloid progenitor cells in the bone marrow.

**Why the Correct Answer is Right**
The myeloid lineage can be identified by various markers, but one of the most specific and widely used markers is CD15. CD15, also known as Lewis X, is a carbohydrate adhesion molecule that is expressed on the surface of myeloid cells. It is involved in cell-to-cell interactions and is an important marker for identifying myeloid lineage cells in flow cytometry and immunohistochemistry.

**Why Each Wrong Option is Incorrect**
* **Option A:** CD3 is a marker for T lymphocytes, not myeloid lineage cells. It is involved in the T cell receptor complex and is used to identify T cells in flow cytometry.
* **Option B:** CD19 is a marker for B lymphocytes, not myeloid lineage cells. It is involved in the B cell receptor complex and is used to identify B cells in flow cytometry.
* **Option C:** CD34 is a marker for hematopoietic stem cells, not myeloid lineage cells. It is involved in cell adhesion and is used to identify hematopoietic stem cells in flow cytometry.

**Clinical Pearl / High-Yield Fact**
CD15 is a useful marker for identifying myeloid lineage cells, especially in the context of acute myeloid leukemia (AML). It is often used in conjunction with other markers to diagnose AML and to identify the specific subtype of the disease.

**Correct Answer:** D. CD15.