I don't nuderstand the meaning of "di" !! "Lui risponde no" is not right ??
OK, I can explain this one. The thing is, there is no reliable one-to-one correspondence between these Italian particles (like "di," "da" or "of," "by" etc), so you can never assume that, just because in many situations "di" is transated as "of," it will be always translated this way. If you make such an assumption, you will always be confused. In this case, think of "di" meaning (kind of) "with," as if in Italian, instead of saying "He replied 'yes'" you had to say "He replied with 'yes'." It actually kind of makes sense that way.
'Di' is used after certain verbs and adjectives. ''Rispondere di no'' means.. to say* no. So I think it's just one of those things that you need to remember.
Di = by; so, maybe another way to look at it would be: He answers by saying no.
To understand better, you can make an analogy: Everytime I ask him to go to the movies, he answers THAT he can't go. He answers [THAT] no. <-- This "[THAT]" is not used in English, that's why it sounds strange to say "di no" in italian. I understand that the "no" is replacing the "he can't go", so that's why we use "di" in italian.
In other languages this happens as well: I think so Io credo di sì (italiano) Eu penso que sim (português) Je pense que oui (français) Yo creo que sí (español)
Because "says" has a different term "dice". Think of it like this "He responds with no"
In italian you say: credere DI si (believe yes); credere DI no (believe not); dire DI sì (say yes) and dire DI no.
They must have fixed it, because I wrote "He responds with no" and it was accepted.
The reason why your answer is wrong is because you used a past-tense version of the term "respond". The correct way to phrase this is "he responds no". Although that is a bit awkward, because no one talks like that anymore, it is grammatically correct.
I wrote ... His answer is no .. Is this ok? It was marked wrong for Duolingo
The sense is the same, but the purpose of this sentence is to focus on the verb, so the action not on the subject (the answer). Rispondere is a verb so you can't really translate it as a noun.
Same for me. Better English would have quotation marks around "no", even if the "no" were given by a letter or a hand-signal. "He responds no" is just bad English. Given that DL doesn't seem to care about punctuation, I wonder why it's caring in this one instance.