add score when collide with gameobject

hi guys i need some help here. I want to destroy my collided object only when the respective key is pressed. but i can detect the get key down on onCollisionEnter??? here's my code thanks in advanced!

IEnumerator OnCollisionEnter(Collision col) {

     //Debug.Log (("") + col.gameObject.name);

     if(col.gameObject.tag == "destroy")
     {
         gameObject.GetComponent<Renderer>().material.color = Color.yellow;


         if(col.gameObject.name=="Drop_(3)(Clone)" && Input.GetKeyDown(KeyCode.D)) 
         {
         
         Destroy(col.gameObject);
         gameObject.GetComponent<Renderer>().material.color = Color.white;
         Debug.Log ("hi");
         
         }