Answer: The first one I think
Explanation: because i feel like it’s right I have a gut feeling
B, you don't have to include information of the author (you).
Principal,
We will dearly miss you. You have not only made this school great, but you have also made us, the students, great. We thank you for all your hard work and dedication that you put into this school. We wish you farewell and hope you enjoy your retirement.