Resolutions duplicates in options menu

I am getting some resolutions duplicates because of the HZ. How can I make a system that detects the lowest hz in the resolutions profile with this code?

  using System.Collections;
  using System.Collections.Generic;
  using UnityEngine;
  
   namespace AkshayDhotre.GraphicSettingsMenu
    {
   /// <summary>
   /// Inherits from the Option class
   /// This class handles the resolution options
   /// </summary>
   public class ResolutionOption : Option
    {
     
     private void Awake()
     {
         Initialize();
     }

     private void Initialize()
     {
         GenerateResolutionSubOptions();

         //Assign the first element from the suboption list as the current option
         //We check if the current suboption is null because if we load the data from the xml file, the currentsuboption will be assigned 
         //and we don't want to reassign it.
         if (currentSubOption.name == "" && subOptionList.Count > 0)
         {
             currentSubOptionIndex = 0;
             currentSubOption = subOptionList[currentSubOptionIndex];
             
         }

         UpdateSuboptionText();
     }

     /// <summary>
     /// Applies the resolution settings
     /// from the xml file
     /// </summary>
     public override void Apply()
     {
         GraphicSettingHelperMethods.ChangeResolution((int)currentSubOption.vector2Value.x, (int)currentSubOption.vector2Value.y);
     }

     /// <summary>
     /// Gets the available resolution from Screen.resolutions and creates the suboptions list containing the availables resolutions
     /// </summary>
     private void GenerateResolutionSubOptions()
     {
         //Clear/Empty the list
         subOptionList.Clear();


         //Cycle through each resolution in Screen.resolutions and create a new suboption with the corresponding names, values and the index
         //Then add that suboption to the suboption list
         int i = 0;
         foreach(Resolution r in Screen.resolutions)
         {
             SubOption t = new SubOption();
             t.name = r.width.ToString() + "x" + r.height.ToString();
             t.vector2Value = new Vector2(r.width, r.height);
             t.indexInList = i;
             subOptionList.Add(t);
             i++;
         }
     }

     /// <summary>
     /// Goes through the list of the resolution and then finds the suboption which has value equal to the input value
     /// and assigns that sub option as the current sub option
     /// </summary>
     /// <param name="v"></param>
     public void SetCurrentsuboptionByValue(Vector2 v)
     {
         if(subOptionList.Count > 0)
         {
             foreach(var t in subOptionList)
             {
                 if(t.vector2Value == v)
                 {
                     currentSubOption = t;
                     currentSubOptionIndex = t.indexInList;
                     UpdateSuboptionText();
                     return;
                 }
             }

             //If no item is found then we use the fall back option
             Debug.LogWarning("Suboption with value : " + v + " ,not found in :" + gameObject.name + ",using fallback option instead");
             currentSubOption = fallBackOption;
             currentSubOptionIndex = fallBackOption.indexInList;
         }
         else
         {
             Debug.LogError("No items in suboption list : " + gameObject.name);
         }
     }
 }

}