Translation:It took eight days.
The fourth and the eighth sound very similar, but they are not the same. I forget which has the longer 'u'.
I believe the eighth day (八日) is pronounced ようか (youka), while the fourth day (四日) is よっか (yokka). I hope this helps!
はい。ありがとうございます! I can really hear the differences in the examples on forvo now! If only I can remember which is which...
Make your own mnemonic rule. Eight is more than four, and it takes more strokes to write ようか than よっか...
It gave me the word "eighth" as an option and I didn't notice the final "h" until my answer was marked as wrong T-T
People, always check all the options before submitting the answer
4th has a little tsu (yokka), 8th has a longer "u" sound (youka), for anyone confused.
"the eighth" (of a month) and "eight days" are the same word in Japanese, 八日, ようか.
The only one that's pronounced differently is 一日, which is ついたち for "first day of the month" and いちにち for "one day".
Perhaps "it takes until the eighth" would be written "あの 八日 まで かかりました"? to emphasise the difference. Thanks Ginkkou for the tip