Choose the correct synonym for ”redoubtable” from the options given below.

The correct option is formidable.

Step-by-Step Explanation:

1. Understanding the Word: The word "redoubtable" is an adjective used to describe someone or something that inspires fear, awe, or respect, often because they are large, powerful, or highly competent (e.g., "a redoubtable opponent"). It comes from the Old French word redouter, which means "to dread."

2. Analyzing the Options:
- flimsy: Means weak, fragile, or easily damaged. This is the opposite of redoubtable.
- perplexing: Means confusing or puzzling. While a redoubtable opponent might be difficult to defeat, the word itself does not mean confusing.
- formidable: Means inspiring fear or respect through being impressively large, powerful, intense, or capable. This directly matches the definition of "redoubtable."
- voluble: Means talking fluently, readily, or incessantly. This is unrelated to redoubtable.

3. Conclusion: Since "formidable" and "redoubtable" both describe something or someone that commands respect and inspires awe or fear due to their power or strength, they are synonyms. Therefore, "formidable" is the correct choice.