Choose the correct adverb to fill in the blank:

Sentence: The scientist faced many obstacles. Yet, she __ persevered, achieving a groundbreaking discovery.

tirelessly

Answer: (3) tirelessly

 Explanation: This question looks for an adverb describing how she persevered.

• Happily suggests a positive but irrelevant emotion to overcoming obstacles.
• Carelessly implies a lack of effort, the opposite of perseverance.
• Tirelessly emphasizes her unwavering and persistent effort.
• Cautiously suggests carefulness, which isn't the main focus here.