This seems wrong should be "a grape" and not grapes (un strugure)
FYI, I don't know when you posted this comment (can't see the dates in my mobile), but Duolingo did give me 'a grape' as the correct answer.
Is the audio a bit weird in the "Tu ai" part for anyone else?
Yeah. It sounds like the two words are recorded separately and put together without enough spacing also sounding a bit robotic.
18 apr 2020 stil "a bunch of grapes"
Oh puhleeeze ... in Romania the word Pruna applies to a variety of fruits where in the USA we have different names. The word applies to what Americans call Prunes and Plums and Pluots and related things.