An alternate answer that is provided uses "Conosciamo", but I thought that "conoscere" was only used when referencing knowledge of personal relations? Are there cases when both are interchangeable?
conoscere is to know people, places and things (and meet people) while sapire is to know facts and skills. Admittedly there does seem to be some overlap in these things, i.e. is knowing an answer the same as knowing a fact? Duo says no.
"i rispondi" isn't a correct traslation of "the answers". You have to traslate that with "le risposte", as did doulingo.
The traslation "già sappiamo le risposte" is also correct, even though the sense of the clause changes a little bit in something of more sad and hopeless.