In the linked structure implementation of list shown in the following figure, which of the following statements can remove the node containing element 30 and release the memory space correctly? 30 50 head ho head->next = head->next->next; NodeType* ptr = head->next; ptr = ptr->next; delete ptr: NodeType* ptr = head->next; head->next = ptr->next; delete ptr; NodeType* ptr = head; head->next = ptr->next; Which of the following statements can add a new node pointed by new node in front of the node containing 30 correctly? head 30 50 new_node 10 Which of the following statements can insert the node pointed by the pointer cur after the node pointed by the pointer ptr into the list correctly? struct Node Type { T data; Node Type* prev; Node Type* next; NodeType* ptr, cur; 104 30 40 ptr cur 20 Which of the following statements can remove the node with the value 30 pointed by cur from the list and release the memory space occupied by this node correctly struct Node Type { T data; NodeType* prev; NodeTypenext; NodeType* cur; 10 50 30 cur