Your translation is incorrect English - should be "eats a banana"
I think they should add "uma banana" or "a banana" even "daquele banana" because without that it wouldn't be grammatically correct in English.
"The monkey eats banana" is incorrect in English. We can say "The monkey eats A banana" or we can say "The monkey eats bananaS." But it is incorrect as it stands now.
"The monkey eats banana" is technically correct English, it's just not a common way to say it. Just as you could say, "The boy eats cake", it's more commonly phrased as "The boy eats a slice of cake" or "The boy eats some cake".