How Restrict in Angular Chosen Remove Selected Data

Question

Hi,

      See the below picture,here i am using angular chosen multi select. if I want to remove the value from index.how can identify the actual values and how to stop Removing from index.

 

e.x => if i am going to remove the "Aluminum Cased Low Grade" .here i want to find

               

               1. Aluminum Cased Low Grade's id?

               2.Some of the reason don't allow to remove form chosen?