Given the task definition, example input & output, solve the new input case.
In this task you will be given an answer to a question. You need to generate a question. The answer given should be a correct answer for the generated question.
Example: This list contains the top 25 accounts with the most followers on the social photo-sharing platform Instagram. As of May 2018, the most followed user is Instagram's own account, with over 235 million followers. Selena Gomez is the most followed individual, with over 137 million followers. Ten accounts have exceeded 100 million followers on the site.
Output: who has the maximum number of followers on instagram
The answer is talking about the Instagram accounts that have the most followers. The question asking about the maximum number of followers. So this is a good example.

New input case for you: The core is the only region in the Sun that produces an appreciable amount of thermal energy through fusion; 99% of the power is generated within 24% of the Sun's radius, and by 30% of the radius, fusion has stopped nearly entirely. The remainder of the Sun is heated by this energy as it is transferred outwards through many successive layers, finally to the solar photosphere where it escapes into space as sunlight or the kinetic energy of particles.
Output:
the long term source of energy that powers the sun is