Correct Answer: Indefatigable

Solution : The correct choice is the first option .

Indefatigable originates from fatigue , which means a feeling of constant exhaustion, and it is used to describe someone who shows untiring effort and remains diligent all the time. This makes it the correct one-word substitute for "one who does not get tired easily".

The meanings of the other options are as follows:

• A pedantic person is someone who gives too much attention to small details.
• A recluse lives alone and avoids going outside.
• A libertine person is one who has low moral values and has too many relationships with many people.