Nā wāhine = "the women". I think the purpose of this example is to show that the kahakō over the "a" in wāhine is used to indicate plural. This is mentioned in the tips & notes for the skill.
There isn't any technically correct answer, since the question gives "women," which is the plural form of "woman," and all of the answers are singular, they all lack na.
Is the plural "wāhine" pronounced differently than the singular "wahine" because of the accent mark on the "a"?
'Ae / Yes - the initial wā is pronounced for two split seconds instead of one. That is what that macron does for all the vowels, actually.
Not necessarily. Women is wāhine instead of wahine for woman. Note the macron over the a for plural. Nā wāhine means the women specifically, and the word nā is not needed in the case of He mau wāhine - some women.
I'm having issues with no luck in getting the kahako where it belongs when I answer a question...therefor ut keeps telling me to watch my accents...