Vowel sounds of adjacent words often "flow" together in Italian. It also depends on who is speaking, how fast, and how clear the sound is (not duolingo's strong point). I often listen to the slow version just to be sure I'm not missing something like this--after a few wrong answers because I didn't hear correctly).
"Tazze" are mugs or coffee cups. "Bicchieri" are cups or drinking glasses. English uses "cup" for both, but they are different types in Italian. I sometimes find it helpful to do an image search for the Italian words (look up "tazze" or "bicchieri" on Google images or a similar site) to get an idea of the difference for words where the English translation overlaps.
The Italian sound (the lady who pronounces the words etc.) is REALLY awful. Each of the other courses on duolingo are OK, but this just sounds bad and incorrect. Also, in many cases the prononciation is rather that of an american Italian woman, than a real Italian one. So maybe there could be found a different audio set for Italian? (Many unclear prononciations, the technical cuts are really bad - in the first lessons I thought some woman with heavy asthm is speaking...) A real disappointment, the Italian audio... :(
I am not Italian myself, so my pronunciation would be of a foreigner, too. (Though I studied Italian for 5 years at university, but it was a long time ago.) I think that the purpose here is to learn from reliable sources - that including the sound and the pronunciation of the language. While the other courses have a quite good audio set for the pronunciation (as far as I can realize and judge), this one really is of a far inferior quality - but you could see that from the many comments regarding it (from other users who follow the Italian language course here on duolingo). - And I think it shouldn't so hard to find a proper audio set - I think all of the other sets are borrowed from other language courses, and modified. I might be wrong, though... Maybe this was cheaper, I don't know. An editor or Duolingo staff member could only clarify that...
It always keeps these sort of words in check for me to remember that most of the time, when you're learning about plurals in Italian, the plural will end in -i, opposed to the singular original word. For example, Il Cane changed to a plural would be Il cani, same with cats. ( Gatto = Gatti )