**Core Concept**
The detection of blood stains involves identifying specific components or markers present in blood. The most specific test for detecting blood stains would involve a highly sensitive and specific marker that is unique to blood.

**Why the Correct Answer is Right**
The correct answer is based on the detection of hemoglobin, a protein present in red blood cells that carries oxygen. The most specific test for detecting hemoglobin is the **Kastle-Meyer test**, also known as the **Kastle-Meyer test for hemoglobin**. This test involves the use of phenolphthalein to detect the presence of hemoglobin, which produces a pink color when reacted with the reagent.

**Why Each Wrong Option is Incorrect**
**Option A:** The **Luminol test** is used to detect the presence of iron in blood, but it is not as specific as the Kastle-Meyer test for detecting hemoglobin.
**Option B:** The **Ammonium persulfate test** is used to detect the presence of hemoglobin, but it is not as sensitive as the Kastle-Meyer test.
**Option C:** The **Hemochromogen test** is used to detect the presence of hemoglobin, but it is not as specific as the Kastle-Meyer test.

**Clinical Pearl / High-Yield Fact**
The Kastle-Meyer test is a highly specific test for detecting hemoglobin, but it can be inhibited by the presence of certain substances such as hydrogen peroxide and bleach. This is an important consideration when using this test in forensic investigations.

**Correct Answer:** C. Kastle-Meyer test