I am trying to install Percona Xtrabackup to my Ubuntu 12.04 LTS insatlled on Amazon EC2. I am trying to follow instruction on the Xtrabackup installation page here. The instruction follows as

Add this to /etc/apt/sources.list, replacing squeeze with the name of your distribution:

deb http://repo.percona.com/apt squeeze main
deb-src http://repo.percona.com/apt squeeze main

In my case I will replace squeeze with precise but when I open /etc/apt/sources.list for editing it says the following

It is suggestion three alternatives instead of editing which are listed a.), b.) and c.).

My Question

What should I do to install Percona Xtrabackup to my box?