How can we check whether an Oz function is tail-recursive?
a. by checking whether there are less than two recursive calls in the body of the recursive function;
b. by checking whether it runs fast enough for some input data and does not have infinite calls;
c. by converting to the kernel language and by checking whether the recursive call is the last expression in the body of the recursive function;
d. by checking whether the recursive call is the last expression in the body of the recursive function;
e. none of the above.