The perfect recursion explanation doesn't exi-
This multiple choice question is pure genius. Options A, B, and C all point to "the answer choice below this one" creating an infinite loop that perfectly embodies recursion's endless self-referential nature. Only option D breaks the chain with an actual definition.
Somewhere, a CS professor is cackling at their desk while students have existential crises during the exam. That base case couldn't come soon enough!