"They are eating rice."
Translation:Ze eten rijst.
If you want to use zijn you also need aan het.
Ze zijn rijst aan het eten.
Because in Dutch the "continuous" (zijn + aan het + infinitive) is only used for emphasis that it is happening now. The "simple present" zij eten can be translated to the simple present and present continuous in English.
My answer was the following:
"Zij eten rijst."
When does one know when to either use "ze" or "zij"?
The "Tips and notes" section mentioned the following:
*Je, ze and we are un-emphasized forms of jij, zij and wij. The difference will be taught in another skill.
However, since it won't be explained until a further lesson, but yet it already expects us to know now how to translate it, hence I'm asking ahead of time.