Translation:Molecules in the air
Interesting that the audio definitely sounds like MO-LE-KYU-LI but if you type that, Duo says you have a spelling error and that the word is "Molekuli". If that is true, then it should be pronounced MO-LE-KU-LI, just as one would pronounce the word "Kuli" -- a dock worker, or coolie (a word now considered dated and offensive in English). Not sure if the Swahili word "kuli" has negative connotations as well. Would need a native speaker's opinion on that.