"His big dogs."
Translation:Ses grands chiens.
Ses grands chiens doesn't accurately translate the sentence. In the English we know the gender of the owner of the dogs. In the French we still don't know the gender of the owner because the pronoun must agree with the object of ownership rather than the subject. This is true whether it was singular or plural.
Referring to a single female dog it would read Sa grosse chienne even though it is his dog.
I'm not complaining because I realize that this is teaching moment but I'm wondering how to actually translate the sentence. There are many occasions in English where it is the pronoun that actually gives the context of gender so how to do that in French.
There must be some way to directly indicate the gender of the subject of ownership in French.
The sentence is correct.
Ses = plural for both masculine and feminine.
But it doesn't accurately translate the sentence. The sentence (in English) stipulates the gender of the owner of the dogs. The French translation does not.
It may be a grammatically correct statement in French. It may be commonplace to use such constructions in French. It may be the only simple way to write it in French. But.... it does not convey the meaning of one of the three English words.
Changing the phrase from plural to singular makes the discrepancy even more apparent. Doing so can actually reverse the meaning of the English phrase. His big dog can translate into Sa grosse chienne/ Her big dog. Of course sa can also mean his but the English requires his only, which the French translation given here does not fulfill.
Again, as can be seen from my previous comment, I'm not complaining about Duo's usage. What I'm wondering is how would such a phrase be accurately translated.