class QueueLL private: struct Node int key; Node *next; Node* queueFront; Node* queueEnd; public: QueueLL QueueLL O bool isEmpty(); void enqueue (int key); void dequeue () int peek ) void printg); l: oid QueueLL: :enqueue (int key) Node *nn new Node; nn->key key; nn->next - nullptr; if (isEmpty )) queueFrontnn; queueEnd = nn; elset queueEnd->next nn; What is the problem in this enqueue function? Select one: a. New element doesn't be pointed b. QueueFront doesn't always point to the first element c. QueueEnd doesn't always point to the last element d. This function works without any