What is wrong with this piece of Prolog code?
ancestor(A, D) :- ancestor (A, P), ancestor(P, D).
Answers:A.
It does not have a definition of the size-N problem.
B.
It has two size-M problems with different sizes.
C.
It does not have a stopping condition.
D.
It is not a tail-recursive program, and it is not efficient.
Answer. C.