In a singly linked list, the next in the last node is equal to O a. null b. the previous node c. the first node in the list d. the last node in the list In a doubly linked list, the next in the last node is equal to a. the last node in the list b. the first node in the list c. the previous node d. null In a circular linked list, the next in the last node is equal to a. the last node in the list b. the first node in the list c. the previous node d. null