Prevention is the best. will be the superlative degree as better is the comparative degree.
or it can be prevention is good(positive degree)
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Better is in comparative degree as it is comparing one from another so its superlative degree is best and positive degree is good.
comparative degree-
prevention is better than cure
superlative degree-
prevention is best
positive degree-
prevention is good
but most appropriate is comparative degree as it shows comparison between prevention and cure.
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