It says "Another correct solution:Bye-bye!" In my opinion, using "Jó napot" for saying goodbye is rather old-fashioned, something you can only hear in pre 1960 films.
If Jo means "good" and napot means "day" why are the options Hello, no , and bye?
Day is "nap". You have to decline it into "napot", the accusative, so that "(I wish you a) good day" translates into "Jó napot (kívánok)". Jó napot is valid from mid-morning until the evening. :)
In the last few exercises of this first basic lesson, the word "jó" offers no possible translation, by lacking the option "good" as a direct translation, and presenting instead others non related words like "wine", "unfortunately" or even twice the word "hello". There is no way of submitting a correct answer like this, and strangely these are repetitions of the same exercise, but with the wrong sugested words for the translation
"Jó reggelt" is "good morning" and is valid to about 9am (my uncle insists it is no longer morning after 8am in the summer when you have already been working for 4 hours!) "Jó napot" is "good day" - used late morning until evening.
Then "jó reggelt" is like "good afternoon"? if so, can you use if for "hello" even when it's out of the afternoon hours?
No - "jó reggelt" is used in the (early) morning. Late morning and afternoon you'd use "jó napot"
Sorry, I meant "Jó napot". My question is: can you use "good morning/good afternoon/good evening" as "hello" respectively in the morning, afternoon, and evening?
Yes, you can. Younger people tend to just use "szia" - but even they will use good morning/good afternoon/good evening as hello (especially with older people).
Technically (it means "I wish you a good day") - but it is reasonably formal. If you'd use "have a nice day" to strangers - then yes.