Which of the following can be the base case for the recursive implementation used to find the length of linked list?

[answerhappygod]

#include<stdio.h>
#include<stdlib.h>
struct Node
{
int val;
struct Node *next;
}*head;
int get_len()
{
struct Node *temp = head->next;
int len = 0;
while(temp != 0)
{
len++;
temp = temp->next;
}
return len;
}
int main()
{
int arr[10] = {1,2,3,4,5}, n = 5, i;
struct Node *temp, *newNode;
head = (struct Node*)malloc(sizeof(struct Node));
head->next = 0;
int len = get_len();
printf("%d",len);
return 0;
}
a) if(current_node == 0) return 1
b) if(current_node->next == 0) return 1
c) if(current_node->next == 0) return 0
d) if(current_node == 0) return 0