It wants "the cheeses are old" instead of an also correct "the cheese is old." I get that "cheeses" is allegedly a correct plural form according to some know-it-alls like Miriam Webster (and yes I get that עגבניות. is in plural form). But cheese is uncountable. How do we know? Example: How much cheese would you like? one cheese please. Nope. That's uncountable without more (e.g. how many wheels, cubes, wedges, or slices of cheese). Uncountable nouns should not have an s in plural form (or at least you are correct when you don't use an s for plural)...I'll stop rambling now if Duolingo marks my answer "you are grammatically correct (but we'd like you to acknowledge the plural Hebrew form)"