**Core Concept**
Anemic hypoxia occurs when there is a deficiency in the amount of hemoglobin or red blood cells in the blood, leading to inadequate oxygen delivery to tissues and organs. This type of hypoxia is characterized by a low oxygen-carrying capacity of the blood.

**Why the Correct Answer is Right**
Anemic hypoxia is primarily due to a decrease in the number or function of red blood cells, leading to a reduced capacity for oxygen transport. This can result from various causes, including anemia due to iron deficiency, vitamin deficiency, or chronic disease. The reduced oxygen-carrying capacity of the blood impairs the delivery of oxygen to tissues, resulting in anemic hypoxia.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect as ischemic hypoxia occurs due to inadequate blood flow to tissues, not a deficiency in oxygen-carrying capacity of the blood.
**Option B:** This is incorrect as histotoxic hypoxia occurs due to the presence of substances that interfere with cellular oxygen utilization, not a deficiency in oxygen-carrying capacity of the blood.
**Option C:** This is incorrect as high-altitude hypoxia occurs due to a decrease in atmospheric oxygen levels, not a deficiency in oxygen-carrying capacity of the blood.

**Clinical Pearl / High-Yield Fact**
It's essential to note that anemic hypoxia can be caused by various factors, including chronic diseases, nutritional deficiencies, and certain medications. A thorough medical history and physical examination are crucial in diagnosing the underlying cause of anemic hypoxia.

**Correct Answer: D. Anemia**