In the sentence "Sound travels better...", the word "better" modifies the verb "travels", hence it functions as an adverb.

১. In option (ক), it modifies the noun "weather", so it is an adjective.
২. In option (ঘ), "to better" is used as a verb meaning to improve.
৩. In option (গ), "better" is a comparative adjective used after a linking verb.

অতিরিক্ত তথ্য: The same word can function as different parts of speech based on its context.