Learn Spanish (Latin America): Sin duda es la mejor opción. - Without a doubt it is the best option.

Because sin duda means "without a doubt"—it expresses complete certainty! In Spanish, declarations of certainty or fact trigger the indicative mood. You would only use the subjunctive if you used one of the adverbs that introduces actual uncertainty, such as tal vez sea la mejor opción (perhaps it is the best option).

Why does mejor come before opción instead of after?

While most descriptive adjectives follow the noun in Spanish, comparative and superlative adjectives like mejor (better/best) and peor (worse/worst) are exceptions. They almost always come right before the noun they describe.

How do we know la mejor opción means "the best option" and not just "the better option"?

Spanish uses the same word, mejor, for both "better" and "best." The definite article (la) combined with the context tells you it is the superlative ("the best"). If you simply wanted to say "it is a better option," you would use the indefinite article instead: es una mejor opción.

Is it ever correct to say sin dudas in the plural?

Yes, sin dudas is grammatically correct and you might hear it occasionally. However, the singular sin duda is a fixed phrase and is far more common and natural-sounding in everyday speech.