"Even though I am small, my body is strong."

Translation: Walau saya kecil, badan saya kuat.

[Rick392366]

"Walaupun saya kecil, badan saya kuat." = not accepted

Dear Duolingo, would you please be so kind to accept this as an alternative correct answer ?
"walau"= "walaupun" , mean the same.
https://kbbi.web.id/walaupun

[PaulGilbert731]

Why is badanku not acceptable?

[Haakon388572]

You probably used "saya" earlier in the sentence, so you would be mixing two levels of formality.