假设 head != nullptr，下面是实现单向循环链表在头节点后插入新节点的代码，横线处应填入（ ）。
struct Node {
int val;
Node* next;
};
void insertAfterHead(Node* head, int x) {
Node* newNode = new Node;
newNode->val = x;
______________________ // 在此处填入代码
}
- A. ```cpp
newNode->next = head;
head->next = newNode;
- **B.** ```cpp
newNode->next = head->next;
head->next = newNode;
- C. ```cpp
head->next = newNode;
newNode->next = head->next;
- **D.** ```cpp
newNode->next = head->next;
head = newNode;