"Is she American?"
Translation:¿Ella es americana?
It's a strange word order. When you ask a question that doesn't contain a question word, the most natural orders are "subject + verb + complement" and "verb + complement + subject".
Duo should have looked over that. Just remember to capitalize everything that needs to be capitalized. You can't expect Duo to know everything.
The simple way i remember is all the 'o' ending words are male and the 'a' is female ... niño (male) americana (female)
Each word has a masculinity assigned to it. So if You are asking if a female if from there then You use the female form and if you ask if a male is from there use the masculine form.
Adjectives ending in -o or -a must be changed to agree with the gender of the noun.
In the question Anericana vs. Americano it is my understanding that it is the same rules as nina vs nino. Hope that helps.
the use of americano is incorect as americano refers to anyone from the continent of america (north or south) the corect word is estados unidos (united states)