How to appear task approver in email notification ?

Hi all, When I maintain PO email notification template by "Maintain Email Templates" APP, I find noAvailable Variableswhich can appear task finisher(approver) as attachments 1&2. I tried four variables to appear task aoprover like attachment 3, and the actual notification appearance didn't appear approver like attachment 4. I want to ask if there is another way to appear task approver in email notification ? Best Regards！ Brandy Zhou.