"This is a food that we must not waste."
Translation:C'est un aliment qu'il ne faut pas gaspiller.
I've done a little research on this. Usually people say de la nourriture and it means "food" in general. People say un aliment and it means an ingredient or foodstuff, like a carrot or an egg. See here, especially the comment by Schmorgluck:
"Nourriture is more general, and more prone to be used with partitive articles (we will more likely say "de la nouriture" than "une nourriture" - the latter is not unknown, but is rarely used literally). Now, in "nourriture" you have "plats" (dishes) and, well, "aliments", the simple things that don't qualify as dishes. It's not that simple, but that's roughly it."
Out of curiosity I hit Google translate with the English version, and this was its answer, so it's possibly right? (I'm never sure how much stock to put in GT's translations - I usually use them as guides from another language into English, but if desperate, I will give it a go and so far, it's been reasonably reliable. Whether DL agrees us another matter!)
Btw, "nous ne devons pas gaspiller" is accepted by DL.
The correct translation provided looks fine. But this lesson seems to focus on the use of "dont" so I wrote: "Ç'est un aliment dont nous ne devons pas gaspiller." This makes sense to me in terms of the other phrases in this lesson, but was marked incorrect. Anyone know why?