"The man asked and nobody answered."

Translation: Mężczyzna zapytał, a nikt nie odpowiedział.

[polikoi]

"a" in this sentence doesn't sound natural for me

[br0d4]

AND = "A" when there is any type of contradictory between both parts:

• "I love you and you love him" - "Ja kocham ciebie a ty (kochasz) jego."
• "He cooks and she cleans the house" - "On gotuje a ona sprząta dom"
• "She is young and he is old" - "Ona jest młoda a on (jest) stary." (In the phrases containing contradiction, the repeated verb can be omitted). BUT: {@style=color: red} if the contradiction is not real, you only use different words to describe similar state, you go into nuances: "He is old and she is also not quite young" - "On jest stary a ona też niemłoda" (there is however some age difference between them, so she is younger than him) or "On jest stary i ona też niemłoda" (they are pretty similar, only you want to be polite and do not use the word "old" to describe a woman).
• "Her blouse is white and her skirt is red" - "Jej bluzka jest biała a jej spódnica (jest) czerwona." - it is so when the used verb is concerns the clothes itself, not the person who wears them; It works the same for longer lists: "Her hat is blue, her blouse is white, her skirt is red and her shoes are black" - "Jej kapelusz jest niebieski, bluzka biała, spódnica czerwona a buty czarne." see also below {@style=color: red}

AND = "I" when there is clear connection or similarity of both parts:

• "I love you and you love me" - "Ja kocham ciebie i ty kochasz mnie." (Attention, in this very case it would be also correct "Ja kocham ciebie a ty mnie", to underline sort of dualism: "you"-"me", while usage of i underlines the mutual similarity. With the usage of a, the repeated verb should be omitted).
• "He cooks and she cooks, too" - "On gotuje i ona też." or "On gotuje i ona też gotuje." or "On gotuje i ona gotuje."
• "She is young and he is young" - "Ona jest młoda i on jest młody."
• "Her blouse is white and her skirt is white" - "Jej bluzka jest biała i jej spódnica jest biała." or "Jej bluzka jest biała i jej spódnica też."
• BUT: {@style=color: red} when you enumerate the parts of clothing that somebody wears i.e. it is about the person, and not about the clothes, you rather use i no matter, whether they are similar or different (as there is no contradictory within the person itself, and the verb relates to the person, not the clothing): "She wears a white blouse and a white skirt" - "Ona nosi białą bluzkę i białą spódnicę."; "She wears a white blouse and a red skirt" - "Ona nosi białą bluzkę i czerwoną spódnicę."

[Emwue]

Yeah, and that is pretty much why without other context, I(a native speaker) find this sentence somehow unnatural too - "Mężczyzna zapytał i nikt nie odpowiedział" seems way more natural, because there is clear connection between the two in that there can be no answer when there is no question first. ;)

Sure, it will fit very well when we have some story about wise man answering all questions and there is no answer when the man asks one(so we expect answer after each question, but none is given, thus contradiction and "a"), but in context-less questions on Duolingo, that doesn't work so well.(Read, I tripped on this question when testing out of Polish course. ;) )

[mihxal]

It's natural.

"i" connects accompanying occurrences, happening somewhat one beside the other

"a" connects occurrences in some logical sequence

[peter314078]

What is the difference between nikt and nigdy? Is " nigdy nie odpowiedział" not ok? Thx

[br0d4]

• nikt = nobody, no-one https://www.diki.pl/slownik-angielskiego?q=nikt
• nigdy = never https://www.diki.pl/slownik-angielskiego?q=nigdy

[patriciawo972030]

Do you need "nikogo nie odpowiedział" for the answer? I wrote "nikogo odpowidział" and was marked wrong.

[alik1989]

The negation 'nie' is mandatory and also 'nikogo' is in the wrong case. "Nobody" is the subject of this clause, so it must take the nominative case, wich is 'nikt'.

https://en.wiktionary.org/wiki/nikt#Declension

[br0d4]

The correct form is "nikt (nom.) nie odpowiedział" here http://sgjp.pl/leksemy/#90010/nikt .

The Subject of the phrase is in Nominative. Only if there is also an Object, then the Object is in Genitive: "Jan (nom.) nie odpowiedział" (no Object) , or with other verbs: "Nikt (nom.) mu nie dał ręki (gen.)", Jan (nom.) nie widzi nczego (gen.)" etc.