Yes you can use i for your thesis
I think it would be the answer a
The answer to this is reins, it is reins because this is all filler for you to allow me to put down this answer, its reins.
The purpose for which something is predetermined or destined.
An act of appointing, setting aside for a purpose, or predetermining.
A place to which one is journeying or to which something is sent when the package has reached its destination kept their destination secret.