Object reference is required to access non-static member?

I'm following a tutorial making my first RTS game, I've came across an error which I can't seem to figure out..

"Assets/Scripts/Player/UserInput.cs(11,36): error CS0120: An object reference is required to access non-static member 'UnityEngine.Transform.root'

What am I doing wrong, sorry for noob question, I've posted the UserInput.cs code below.

 using UnityEngine;
 using System.Collections;
 using RTS;
 
 public class UserInput : MonoBehaviour {
 
     private Player player;
 
     // Use this for initialization
     void Start () {
         player = Transform.root.GetComponent<Player> ();
     }
     
     // Update is called once per frame
     void Update () {
 
     }
 
     private void MouseActivity() {
         if (Input.GetMouseButtonDown (0)) LeftMouseClick();
         else if(Input.GetMouseButtonDown(1)) RightMouseClick();
     }
 
     private void LeftMouseClick() {
         if(player.hud.MouseInBounds()) {
             GameObject hitObject = FindHitObject ();
             Vector3 hitPoint = FindHitPoint ();
             if(hitObject && hitPoint != ResourceManager.InvalidPosition) {
                 if(player.SelectedObject) player.SelectedObject.MouseClick(hitObject, hitPoint, player);
                 else if(hitObject.name!="Ground") {
                     WorldObject WorldObject = hitObject.transform.root.GetComponent<WorldObject>();
                     if(WorldObject){
                         //we knowno selected object
                         player.SelectedObject = WorldObject;
                         WorldObject.SetSelection(true);
                     }
                 }
             }
         }
     }
 
     private void RightMouseClick() {
         if (player.hud.MouseInBounds () && !Input.GetKey (KeyCode.LeftAlt) && player.SelectedObject) {
             player.SelectedObject.SetSelection (false);
             Player.SelectedObject = null;
         }
     }
 
     private GameObject FindHitObject() {
         Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
         RaycastHit hit;
         if(Physics.RayCast(ray, out hit)) return hit.collider.gameObject;
         return null;
     }
 
     private Vector3 FindHitPoint() {
         Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
         RaycastHit hit;
         if (Physics.Raycast (ray, out hit))
             return hit.point;
         return ResourceManager.InvalidPosition;
     }
 
 }