#!/bin/bash
# your code goes here
echo "I am testing with sample, use sed -i to make the change permanent into the file"
echo -e "\ncommenting starts\n"
echo -e "option domain-name example.org;\ndont touch me \noption domain-name-servers ns1.example.org\ndont touch this" | sed 's/^option domain-name/#option domain-name/' 
echo -e "\nuncommenting starts\n"
echo -e "#option domain-name example.org;\ndont touch me \n#option domain-name-servers ns1.example.org\ndont touch this" | sed 's/^#option domain-name/option domain-name/'