This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Human leukocyte antigen ( HLA) DR 4 occurs in about 70% of patients with rheumatoid arthritis HLA R4 encoded in the major histocompatibility complex (MEW) region on - 
Select and explain. 
A. Chromosome 6, B. Chromosome 9, C. Chromosome 18, D. Choromosome 22
A: Chromosome 6
Answer: A: Chromosome 6 
Explanation: None