The aspect that can make your code reusable is adding functions. Functions allow you to encapsulate code into reusable blocks that can be called multiple times throughout your program or even in different programs.
The other options, while helpful for understanding the code (adding comments) or for debugging (adding print statements), do not contribute directly to the reusability of the code. Adding required functionalities can make the code more useful, but it's the modularization through functions that primarily enhances reusability.