Translation:Zij eten de tomaat.
When do you use "de" insteadof "het"?
You will have to remember which article goes with which noun, most of the time.
See here for more info: https://www.duolingo.com/comment/3732938
where is are in the sentence. I believe the correct sentence in Dutch should be zij zijn eten de tomaat. because Zij eten de tomaat shuld be they eat tomatoes.
You are almost right. The correct way to translate be +ing is :
Ze zijn de tomaat aan het eten
Whats the difference between ze and zij?
In most cases both are accepted, though with type what you hear exercises only one of the two is accepted. More info: https://www.duolingo.com/comment/3734337
Shouldn't there be a Plural of Tomat ?
How do you mean?
No I mean to say , multiple persons eating single tomato is a bit weird. But I believe, here they are talking about the tomato as a type of fruit but not a literal piece of tomato.
Nothing strange about that, cut a tomato in two pieces and they are eating a single tomato.