When talking about appli de rencontre in the plural, is it applis de rencontre or applis de rencontres? I think I have seen both. If both are valid why is "recontre" pluralized in applis de rencontres since it seems to be a descriptor which in my understand normally takes zero article and stays in the singular?
Duolingo demands Comment la population a évolué globalement? and marked as a mistake my answer Comment la population a-t-elle évolué globalement? Does mine also work? If I dont want to use an extra pronoun, can I also say Comment a la population évolué globalement?