Final answer:
Upon leaving the ER, the vesicle containing the MHC I:peptide complex travels to the Golgi apparatus for modification before being directed to its final destination, such as the plasma membrane.
Step-by-step explanation:
The MHC I:peptide complex is an important component of the cellular process that presents antigens to T cells in the immune response. After the synthesis of the MHC I:peptide, it leaves the endoplasmic reticulum (ER) in a membrane-enclosed vesicle. The vesicle then moves through the cell to reach its final destination.
As part of the endomembrane system, these vesicles are transported to the Golgi apparatus where they are modified. The vesicles fuse with the cis face of the Golgi apparatus and continue through to the trans face where they are sorted, tagged, and packaged. Afterward, this vesicle, which now contains modified proteins or lipids, is directed towards the plasma membrane where it can be embedded into the membrane or the vesicle can release its contents outside the cell.
The correct option that describes this process is: a. Golgi apparatus.