Problem for account creation system

I'm trying to create an account creation system within Unity, but I run into the following error:

error CS0246: The type or namespace name Response could not be found. Are you missing an assembly reference?.

Script NetworkConnection:

 `public void CreateUser(string userName , string email , string pass , Action<Response> response){
         StartCoroutine (Make_CreateUser (userName, email, pass, response));
     }
     private IEnumerator Make_CreateUser(string userName , string email , string pass , Action<Response> response){
         WWWForm form = new WWWForm ();
         form.AddField ("userName", userName);
         form.AddField ("email", email);
         form.AddField ("pass", pass);
 
         WWW w = new WWW ("http://localhost/game/createUser.php", form);
 
         yield return w;
         response (JsonUtility.FromJson<Response> (w.text));
     }
     [Serializable]
     public class Response {
         public bool done       = false;
         public string message = "";
     }`

MenuController script:

  `[SerializeField] private InputField userNameInput     = null;
 [SerializeField] private InputField emailInput         = null;
 [SerializeField] private InputField passwordInput     = null;
 [SerializeField] private InputField RepasswordInput     = null;
 [SerializeField] private Text textInput             = null;

 private NetworkConnection s_NetworkConnection =  null;

 public GameObject Register;

 private void Awake(){
     s_NetworkConnection = GameObject.FindObjectOfType<NetworkConnection> ();
 }

 public void SubmitRegister(){
     if (userNameInput.text == "" || emailInput.text == "" || passwordInput.text == "" || RepasswordInput.text == "") {
         textInput.text = "Please, complete all fields";
         return;
     }
     if (passwordInput.text == RepasswordInput.text) {
         textInput.text = "Loading...";

         s_NetworkConnection.CreateUser (userNameInput.text, emailInput.text, passwordInput.text, delegate (Response response) {
             textInput.text = response.message;
         });
     } else {
         textInput.text = "Passwords are not equals";
     }
 }

 public void OnMouseDown ()
 {
     Register.SetActive (!Register.activeSelf);
 }`

The problem is in the MenuController script in this snippet:

s_NetworkConnection.CreateUser (userNameInput.text, emailInput.text, passwordInput.text, delegate (Response response) {