This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
Which of the following statements best applies to the following diagram? 
Select and explain. 
A. Depicts the cell-membrane MHC product associated with narcolepsy, B. Essential for the transplacental passage of antibody, C. Found on T and B lymphocytes and all nucleated cells, D. Present on macrophages but not neutrophils
C: Found on T and B lymphocytes and all nucleated cells
Answer: C: Found on T and B lymphocytes and all nucleated cells 
Explanation: The figure shown in the question is a schematic representation of the MHC class I molecule, which has a CD8 binding site (a3 ) and a peptide-binding site (a1 and a2 ). MHC class I is active on all nucleated cells.