"Their dog eats."
Translation:Hun hond eet.
A lot of people are asking this question. It's probably because 'zijn' has two meanings. It's either possessive as in 'zijn avondeten' or a plural verb of to be as in 'wij zijn'. Because of it's plural meaning in the verb, I guess people assume a plural possessive meaning as well, so make sure you get this:
Zijn avondeten = His dinner Wij zijn = We are Hun avondeten = Their dinner