The antigen lacking in Rh negative person is ?

**Core Concept**
The Rh blood group system is a complex immunohematological system that determines an individual's blood type. The Rh system consists of multiple antigens, with the D antigen being the most critical. Individuals who lack the D antigen are classified as Rh negative (Rh-), while those with the D antigen are classified as Rh positive (Rh+).

**Why the Correct Answer is Right**
The D antigen is encoded by the RHD gene and is located on the surface of red blood cells. In Rh-negative individuals, the RHD gene is either deleted or mutated, resulting in the absence of the D antigen. This absence makes Rh-negative individuals more susceptible to Rh incompatibility during pregnancy or transfusion. The Rh system plays a crucial role in transfusion medicine, and identifying the correct Rh type is essential to prevent adverse reactions.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify which antigen is lacking in Rh-negative individuals.
* **Option B:** This option is incorrect because it mentions the C antigen, which is a different antigen within the Rh system.
* **Option C:** This option is incorrect because it mentions the E antigen, which is also a different antigen within the Rh system.

**Clinical Pearl / High-Yield Fact**
The Rh system is a vital aspect of transfusion medicine, and understanding the different Rh types is crucial to prevent adverse reactions during blood transfusions. Rh-negative individuals should receive only Rh-negative blood to prevent the introduction of the D antigen and subsequent immune response.

**Correct Answer: D. D antigen**