The sequence for the processing of proteins produced within the cell is...
A) Proteins are broken into fragments, transported to the rough endoplasmic reticulum, fuse with a Golgi vesicle containing class II MHCs, and this complex is transported to the plasma membrane.
B) Proteins are broken into fragments within a vesicle, which fuses with a Golgi vesicle containing class I MHCs, and this complex is transported to the plasma membrane.
C) Proteins are broken into fragments within a vesicle, which fuses with a Golgi vesicle containing class II MHCs, and this complex is transported to the plasma membrane.
D) Proteins are broken into fragments, transported to the rough endoplasmic reticulum, combined with class II MHCs, move to the Golgi apparatus, then to the plasma membrane.
E) Proteins are broken into fragments, transported to the rough endoplasmic reticulum, combined with class I MHCs, move to the Golgi apparatus, then to the plasma membrane.

MHC class I and class II MHC molecules are important for the protein processing and presentation of the molecule. MHC class I molecules has the ability to expresse on all the nucleated cells whereas class II MHC molecules are mainly expressed on the B cells and macrophages ( antigen presenting cells).

The processing of MHC class II molecule involves the following steps. The breakdown of proteins into fragments by the help of enzyme. These fragments are transported to the rough endoplasmic reticulum. From RER, they fuse with the glogi vesicle that contains class II MHC molecule. The complex is then transported to the plasma membrane.

Thus, the correct answer is option (A).