**Core Concept**
Megaloblastic anemia is a type of anemia characterized by the production of abnormally large red blood cells that are not able to function properly. This condition is caused by a deficiency in either vitamin B12 or folate, leading to impaired DNA synthesis and cell division.

**Why the Correct Answer is Right**
Megaloblastic anemia is typically associated with features such as macrocytosis (large red blood cells), hyper-segmented neutrophils, and a normocytic or macrocytic anemia. The correct answer will be a feature that is not characteristic of megaloblastic anemia.

**Why Each Wrong Option is Incorrect**
**Option A:** Macrocytosis is a hallmark feature of megaloblastic anemia, characterized by red blood cells that are larger than normal.
**Option B:** Hyper-segmented neutrophils are a common finding in megaloblastic anemia, indicating impaired DNA synthesis.
**Option C:** A normocytic or macrocytic anemia is a characteristic feature of megaloblastic anemia, reflecting the impaired production of red blood cells.

**Clinical Pearl / High-Yield Fact**
In megaloblastic anemia, the bone marrow is filled with large, immature red blood cells, which can lead to a decrease in the production of other blood cells, including platelets and white blood cells.

**Correct Answer: D.**