Give the plural of these nouns: university, thief, day, sky, ski, party, key, story, taxi, leaf, way, tragedy, language, comedy, knife.  Помогите пожалуйста.

Universities | Thiefs | Days | Нет множественной формы | Нет мн. формы | Parties | Keys | Stories | Taxi's " | Leafs | Ways | Tragedys | Languages | Comedies | Knives
Можно не благодарить