"You must hear this!"
Translation:אתן חייבות לשמוע את זה!
What's the difference between עליך and אתה חייב? Both seem to express a sense of obligation.
You're right, they express the same thing. the difference between them is that עליך is a more offical way of expressing it and in a day-to-day life אתה חייב is being used a lot more commonly.
Why do they mark it wrong if you use a different gender from theirs? How are we supposed to know?
According to what Reverso Context suggests it's okay to use צריך/צריכה here. Is it accidentally not accepted or is it some kind of "street" form?
If by "street form" you mean slang - no, it's not slang. The correct way to say it is "את צריכה לשמוע את זה" (that's the female version).
This is highly unusual for Duo, but it seems they didn't approve all the gender possibilities for this sentence. Furthermore, the proper words for the suggested answer were not even given in the word bank! (אתן חייבות לשמוע את זה!)
I reported it.
Thank you - yes, I understand that, but I had thought that this was a matter of convention - I hadn't realised that writing חיב (or any similar example) without the nikudot was actually regarded as incorrect.
Does this convery an obligation, like a boss or a superior telling his/her employees/underlings you MUST hear this? Or a sort of invitation, like when a friend my tell you, you must hear this? Could it be both?