A kidney-transplant patient experienced a cytotoxic rejection of the new kidney. Place the following in order for that rejection: (1) apoptosis occurs; (2) CD8⁺ T cell becomes CTL; (3) granzymes released; (4) MHC class I activates CD8⁺ T cell; (5) perforin released.
a. 1, 2, 3, 4, 5
b. 5, 4, 3, 2, 1
c. 4, 2, 5, 3, 1
d. 3, 4, 5, 1, 2
e. 2, 3, 4, 1, 5