like many others i'm confused about the usage of 'e' vs. 'ed'. some explain that the 'd' is only added if the following word begins with the same vowel as the one the 'd' is added to (e.g. 'leone ed elefante') but duolingo itself seems to not be following this rule. what gives?
E or ed before uomo or uomini has a reason. This “u”before another vowel ( more open and longer) Like “o” becomes a semivowel or semiconsonant. It is no longer a proper “u” but closer to a “w”. Ed una... is ok because that “u” is just a normal u vowel. In grammars you will find it under “ approximant consonants”