"You love our sons."
Translation:Filios nostros amatis.
The English doesn't necessarily suggest a second person plural. "amas" should be allowed as well as "amatis".
But 'amas' isn't in the list of options. It's not asking you for all possible translations of the given sentence, but simply to match the given words that would form one possible rendering of it. And yes, it's slightly annoying...
If you type, instead of using the given words, you cannot know, while there is a difference between plural and singular. Ergo, si vere tenere velimus rem, oportet aut addere vim pluralem in lingua anglica, aut sententiam singularem Latine.
After studying Latin for the past four years, I'd say that "amatis" is not used as a present tense noun. "Amas" would be the proper word usage. Additionally, I would say "nostros filios" rather than "filios nostros."
But adjectives and possessives generally come after nouns in Latin (carried over into French).
There is no such thing as a present tense noun, only verbs have tense. Amatis is perfectly acceptable. The difference between amas (you singular love) and amatis (you plural love) is not clear in English but both are correct Latin.