JSFiddle - React, Tailwind, and code Playground

HTML

<select id="bu_id">
  <option value="Rupee">India</option>
  <option value="Dollar">US</option>
  <option value="Pound">UK</option>
</select>

<select id="role_id">
   <option value="1">One</option>
   <option value="2">Two</option>
   <option value="3">Three</option>
   <option value="4">Four</option> 
</select>

JavaScript

$('#bu_id').change(function(){
    var val = $(this).val();
    
    $('#role_id option').each(function(){
        var text = $(this).text();       
        text = text.split(' ')[0];
        
        if($(this).is(':first-child')){
            text = text+' '+val
        }else{
            text = text+' '+val+'s'
        }
        
        $(this).text(text)        
    });
    
}).trigger('change');