What does "indefatigable" describe?

The term "indefatigable" is used to describe someone who persists tirelessly, demonstrating sustained enthusiasm and energy in their actions, regardless of obstacles or fatigue. It conveys a sense of unwavering commitment and drive, indicating that the individual continues to work hard and maintain effort over time without becoming weary.

In this context, the other options do not capture the essence of "indefatigable." A indicates a lack of interest or motivation, which is opposite to the idea of sustained effort. B refers to a habit, failing to address the active and enthusiastic nature implied by "indefatigable." D suggests something that cannot be conquered or overcome, which does not align with the positive and relentless enthusiasm associated with the word. Therefore, C accurately encapsulates the definition and spirit of "indefatigable."