"He is your dog, Maha."
Translation:هُوَّ كَلْبِك يا مَها.
Yep, you're right. Someone else also reported that yesterday, but I'm not sure if Duolingo is paying attention to this. The problem is, they are dependent on a text-to-speech machine and i myself not sure how this works but seems it is something out of control when it comes to Arabic and vowels in it.
I see that translation suggests both 'kalbak' and 'kalbik' but only one of this is considered correct. Can you please explain the difference and the usage?
Let's put the audio here aside because it is wrong.
The word in this sentence should be "Kalbuki" (your dog) - speaking to a female (Maha is a female's name). In Arabic it would be كَلْبُكِ
If we are talking to a male (i.e. "your" is for a male person) then it would be كَلْبُكَ (kalbuka) - as you can see the letters are the same but the diacritics at the end are different (-ka when speaking to a male, -ki when speaking to a female).
The main word here is (kalb) كلب (i.e. dog). In this situation and this sentence it is the subject (or in other words, the word is it Nominative case) so it has to be (Kalbu-). I put (-) at the end because this could either be a suffix here or simply Tanwin or Nunation (-un). Just as a bonus, let's suppose it was preceded with a preposition, like "from" مِن (min): from a dog - that would change the ending: مِن كلبٍ (min kalbin). Not sure what they call this case in English, but in Arabic we call it Majrúr مجرور.
Finally, if the word is in Accusative case (some verb is applied to it), then it would get (-a) ending. Example: He sees a dog يرى كلباً (yará kalban). Again, Tanwin or nunation (-an) is used here because the word (كلب: dog) is indefinite.