### Step-by-Step Solution:
1. **Understanding Mendelian Disorders**:
- Mendelian disorders are genetic disorders caused by a defect in a single gene. They can be inherited in a predictable manner based on Mendel's laws of inheritance.
2. **Differentiating Between Mendelian and Chromosomal Disorders**:
- Mendelian disorders involve mutations or defects in individual genes, while chromosomal disorders involve abnormalities in the number or structure of chromosomes (e.g., Down syndrome, Turner syndrome).
3. **Identifying Common Mendelian Disorders**:
- Common Mendelian disorders include:
- **Hemophilia**: A sex-linked recessive disorder affecting blood clotting.
- **Cystic Fibrosis**: An autosomal recessive disorder affecting the respiratory and digestive systems.
- **Sickle Cell Anemia**: An autosomal recessive disorder affecting hemoglobin in red blood cells.
- **Color Blindness**: A sex-linked recessive disorder affecting color perception.
- **Phenylketonuria (PKU)**: An autosomal recessive disorder affecting metabolism.
- **Thalassemia**: An autosomal recessive disorder affecting hemoglobin synthesis.
4. **Analyzing the Options Provided**:
- The question likely provides multiple options, some of which may include both Mendelian and chromosomal disorders.
- For example, if the options include hemophilia, cystic fibrosis, Down syndrome, and Turner syndrome, we can identify which are Mendelian.
5. **Eliminating Chromosomal Disorders**:
- From the options, identify and eliminate any that are chromosomal disorders (e.g., Down syndrome, Turner syndrome, Klinefelter syndrome).
6. **Final Selection of Common Mendelian Disorders**:
- After eliminating the chromosomal disorders, the remaining options will be the common Mendelian disorders.
7. **Conclusion**:
- The most common prevalent Mendelian disorders are hemophilia, cystic fibrosis, sickle cell anemia, color blindness, phenylketonuria, and thalassemia.
