Final answer:
MHC I molecules present endogenous antigens, which come from inside the cell, and are found on the surface of all nucleated cells in the body.
Step-by-step explanation:
MHC I molecules present endogenous antigens. These antigens come from inside the cell, such as viral or tumor proteins. MHC I molecules are found on the surface of all nucleated cells in the body and play a key role in presenting these antigens to the immune system. This helps the immune system identify and eliminate infected or abnormal cells.