"As minhas primas" directly translates to "the my cousins". Why is the As used to beging the sentence here?
I think this may help you: http://www.duolingo.com/#/comment/64947
I think because in this sentence, the cousins are all female.
The "As" is optional
Duo my answer is right.
My answer is the of Duo
Na correção do Duolingo é "My cousins are at the farm".