Translation:Please eat vegetables.
If I recall correctly, a parent is likely to use the less polite ~なさい (polite command) form.
It marked this kanji sentence wrong because I typed 野菜（やさい） in kanji. I've reported it (Jan. 5).
Lots of words are implied in Japanese. Without more context, this phrase could refer to the ones on your plate, or just a request for you to eat more in general.
I think in this context it rather means Please eat vegetables' in general. If some specific vegetables it may say この・その 野菜、because 野菜 is too a vague expression and if you refer some vegetables on your plate, you may say にんじんを食べてください Please eat the carrot. etc...
I think Duolingo requires literal translation word for word, and the word for "some" is not here.
The て-form of verbs lets you express sequences of actions, but it also has many special idiomatic uses. In particular, with ください it's a way of making a request to do that thing. (This is common enough that if you leave out the ください, it's basically implied.)
Could this mean "Please eat your vegetables?" with context? Or is it strictly a general statement?