public List<GameObject> objects;

        int activeObjectIndex = -1;

        void Start()
        {
            NextObject();
        }

        void Update() {
            if (Input.GetKeyUp(KeyCode.K))
            {
                NextObject();
            }
        }

        void NextObject()
        {
            activeObjectIndex = (activeObjectIndex + 1) % objects.Count;
            for (var i = 0; i < objects.Count; i++)
            {
                objects[i].SetActive(i == activeObjectIndex);
            }
        }