Choose from the following to construct the steps of antigen processing to activate CDB T cells in the correct order. (not all steps may be needed)
1. Complex is transported to the cell surface.
2. Complex binds TCRs and causes an immune response.
3. MHC I proteins bind protein fragments.
4. MHC I proteins bind protein fragments.
5. Protein antigens are degraded by proteasomes in the cell.
6. Protein fragments are transported to the ER.
7. Protein antigens are endocytosed by cell.
a. 5, 6, 4, 1,2
b. 5, 6, 3, 1,2
c. 7,5, 6, 4, 2
d. 7,5, 6, 3,2