I'm Polish and didn't choose "Będziemy musieć przeczytać dziewięć książek". Apparently it's correct grammatically but nobody really says so.
"Będziemy musiały/musieli przeczytać..." sounds much more naturally.
Why is it more natural saying it this way?
Nie ma przyczyny. To zwyczaj.
Polish tries to avoid repetition. And musieć przeczytać are two infinitives in a row, which can also easily be avoided.
Is there any difference between musiały and musieli? Native speakers can you explain? Thanks a lot.
In past tense, the gender of the subject of the sentence is always visible. So, "będziemy musiały" will be said by a group consisting of women-only. "będziemy musieli" will be said if there is at least one man among 'us'.
I assumed that that they were all women so why should Duo penalize me for that?
I know that Polish often defaults to the male but I should be credited for any valid alternative. Reported.
Would czytać (With an accent on the final c) and no prze ... be wrong?
It's accepted, but it's really rather unusual. It implies that you will be... in the process of reading nine books? As if you were not supposed to finish them.