Rh factor is

Options

A. An antibody
B. An antigen.
C. A Pleiotropy
D. A polygenic trait

Answer

**Step-by-Step Solution:**

1. **Understanding the RH Factor**: The RH factor, also known as the Rhesus factor, is a specific protein that can be present on the surface of red blood cells. It is important in determining blood types.

2. **Identifying RH Positive and Negative**: If an individual has the RH factor protein on their red blood cells, they are classified as RH positive. Conversely, if the protein is absent, the individual is classified as RH negative.

3. **Analyzing the Options**:
- **Option 1: An Antibody**: This is incorrect because the RH factor itself is not an antibody; it is a protein found on red blood cells.
- **Option 2: An Antigen**: This is partially correct because the RH factor can be considered an antigen, as it can trigger an immune response if introduced into an RH-negative individual. However, this does not fully capture the nature of the RH factor.
- **Option 3: A Pleiotropy**: This is incorrect as pleiotropy refers to a single gene affecting multiple traits, which does not apply to the RH factor.
- **Option 4: A Polygenic Trait**: This is the correct answer. The RH factor is influenced by multiple genes, making it a polygenic trait.

4. **Conclusion**: The RH factor is best described as a polygenic trait, as it involves multiple genes that contribute to its expression and variation in the population.

**Final Answer**: The RH factor is a polygenic trait (Option 4).

---