Is hydrogen the right answer y’all?

The correct answer is hydrogen.

Explanation:

Stars in the main sequence will remain in the main sequence as long as their cores contain hydrogen atoms. This is because main sequence stars run on the hydrogen atoms within their core to prevent them from falling to the force of gravity. Once these hydrogen atoms run out, the star is no longer considered a main sequence star, gravity takes hold, and the star collapses.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.