Hi,

I have created a trigger in task where the creator should recieve an email alert when the task is completed.Here the trigger is working fine.Creator has received the emailalert .But in emailalert  i need to display opportunity name which is related to that task. Here i used WhatId. How do i get opportunity name instead of opportunity id

trigger EmailAlertforTaskCompletion on Task (before update) {
    
    set<String> setownerIds = new set<String>();
    if(Trigger.isUpdate && Trigger.isBefore){
        for(Task objT : Trigger.new){
            if(objT.Status == 'Completed'&& ('' + objT.WhatId).startsWith('006')){
                setownerIds.add(objT.CreatedById);
                
       List<User> lstU = [select id,email from User where Id in : setownerIds];  // limit 1      
       List<String> lstEmails = new List<String>();
       
       for(User objU : lstU){
           lstEmails.add(objU.email);
       }
       
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
        List<String> toAddresses = new List<String>();
        toAddresses.addall(lstEmails);
        mail.setToAddresses(toAddresses);
        mail.setSubject('A task assigned by you has Completed');    // Set the subject
                
        String template = 'Hello, \nYour assigned task has Completed. Here are the details - \n\n';
        template+= 'Subject - {0}\n';
        template+= 'Opportunity - {1}\n';
        template+= 'Due Date - {2}\n';
        template+= 'Priority - {3}\n';
        template+= 'Comments - {4}\n';
        
        String duedate = '';
        if (objT.ActivityDate==null)
            duedate = '';
        else
            duedate = objT.ActivityDate.format();
            
        List<String> args = new List<String>();
        
        args.add(objT.Subject);
        args.add(objT.WhatId);
        args.add(duedate);
        args.add(objT.Priority);
        args.add(objT.Description);
       
        String formattedHtml = String.format(template, args);
       
        mail.setPlainTextBody(formattedHtml);
        Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
       }
     }
    }
}