But in English they are different: w/o "the," it sounds like a claim about all fruit (or at least fruit-in-general)--which is (obviously!) not true; w/ "the," it sounds like a claim about some definite fruit(s)--which may be true or false, depending on the fruit(s) being referred to.
What about in Italian? How is this distinction drawn?
A native speaker on HiNative explains it as:
"la frutta" is plural a word, it is different from frutto/frutti: it has a much wider, more general meaning, a collective name for all fruits
-la mela è un frutto
-mela e pera sono dei frutti (they are two specific fruits)
-la frutta è buona (all fruits are good)
-mi piace la frutta
-mi piacciono tutti i tipi di frutta
-mi piacciono tutti i frutti
a little bit different for verdura (collective name for all edible vegetables) and verdure (another plural, more specific)
-negozio di frutta e verdura
-minestra di verdura a type of soup (it's not a meat soup)
-minestra di verdure a soup with some specific vegetables
-la verdura dell'orto: all vegetables grouped in their uniqueness of garden work products
-le verdure dell'orto: some specific vegetables grown in the garden
As a rough guide. The word 'obvious' translates as 'ovvio.' Adding 'mente' to the end of it - ovviamente - is the same as adding 'ly' in English - obviously. This is true for most adverbial translations. factual = fattuale, factually = fattualmente, lento = slow, lentamente = slowly, etc.. I can see a dictionary giving 'of course' as a definition of 'ovviamente' but I suppose Duolingo's computer is asking for a more exact translation. However, I do agree with you, I think 'of course fruit is sweet' is good translation of the Italian sentence, even if it should be 'Of course THE fruit is sweet.' Buona fortuna!!
I do that already. In the past, Duo will give a definition and then when I go to use it later, it marks it as incorrect. With today's programming, it's easier than ever to get consistency which Duo doesn't seem to be capable of. It's a good program but it could be better.
In my world Obviously the fruit is sweet means that the sweetness of the fruit is a fact, whereas the other, The fruit is obivously sweet, means that it is the taste as such that is apparently sweet. But I may as well be wrong about this. English isn't my mothertongue after all :)