Applying a script to two objects not working

In short, I've got these blocks which, when collided with, generate a random + or - problem e.g 2 - 5. Now I originally only had one of these blocks in the first level but other levels will need more than one. I have been working for hours trying to find a way to allow blockade 1 and 2 to be able to be affected by the script. Once the question is answered correctly, the blockade will be destroyed allowing the player to continue. Here is the code:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 using UnityEngine.SceneManagement;
 
 public class Collisions : MonoBehaviour
 {
     public GM gm = new GM();
     private int N1;
     private int N2;
     private int AnswerCorrect;
     public Text inputfield;
     public Text QuestionBox;
     public GameObject QuestionPanel;
     string opperand;
     public GameObject Blockade;
     public GameObject Blockade2;
     public GameObject Enemy;
     public KeyCode Submit;
 
     void Update()
     {
         if (Input.GetKey(Submit))
         {
             CheckAns();
         }
     }
     public void QuestionMaker()
     {
         string myOperator = GetRandomOperator();
 
         QuestionBox.text = "What is " + N1 + myOperator + N2 + "?";
     }
     public string GetRandomOperator()
     {
 
         int randomOperator = Random.Range(0, 2);
 
         N1 = Random.Range(1, 10);
         N2 = Random.Range(1, 10);
 
         switch (randomOperator)
         {
             case (0):
                 opperand = "-";
                 AnswerCorrect = N1 - N2;
                 break;
             case (1):
                 opperand = "+";
                 AnswerCorrect = N1 + N2;
                 break;
         }
         return opperand;
     }
 
     
     public void CheckAns()
     {
 
         if (inputfield.text == AnswerCorrect.ToString())
         {
             Destroy(Blockade);
             QuestionPanel.SetActive(false);
         }
         else
         {
             QuestionMaker();
         }
     }
     void OnCollisionEnter2D(Collision2D col)
     {
         if (col.gameObject.name == "End")
         {
             Scene scene = SceneManager.GetActiveScene();
             SceneManager.LoadScene(scene.buildIndex + 1);
         }
         if (col.gameObject.name == "Blockade")
         {
             QuestionPanel.SetActive(true);
             QuestionMaker();
             GetRandomOperator();
             CheckAns();
         }
         if (col.gameObject.name == "Blockade2")
         {
             QuestionPanel.SetActive(true);
             QuestionMaker();
             GetRandomOperator();
             CheckAns();
         }
     }
 }

I am well aware that this will not work because I removed all the things I tried so that whoever replies may have a crack at it. Thank you.