Fas ligand and Fas protein receptor promote the aggregation of procaspase-8, which becomes activated, leading to apoptosis.

A) Fas ligand inhibits procaspase-8 aggregation.
B) Fas protein receptor has no role in caspase activation.
C) Procaspase-8 aggregation is irrelevant to apoptosis.
D) Fas ligand and Fas protein receptor contribute to caspase-8 activation.