Cena is a specific meal. la cena = dinner (or supper)
the meal = la comida
Afternoon tea = merinda http://www.wordreference.com/es/translation.asp?tranword=tea
I have the feeling that DL gives you the accepted translation that was closest to what you typed even if it's not the best translation overall. So if you answered "meal", the closest valid translation was "tea". I don't find this system particularly useful, and I always check the discussion page in case of doubt.
I think you misunderstood that comment. The context of that comment was more like "the term cena specifically refers to the evening meal".
The meal terms will be used most always with the definite article in Spanish. You can leave out the article when you're talking about rather general (but not generalised) things involving that meal.
- A veces no puedo comer (la) cena. - Sometimes I cannot eat dinner. (But using the verb cenar instead would sound better in any case.)
Ronita, that is correct. Regular '-ar' and '-ir' verbs will have identical nosotros forms in the Present and the Preterite conjugation:
- hablamos - we are speaking; we spoke
- disfrutamos - we are enjoying; we enjoyed
- salimos - we are leaving; we left
- escribimos - we are writing; we wrote
Note that this isn't true for '-er' verbs. They will have an 'e' in the Present form where they have an 'i' in the Preterite:
- corremos - we are running
- corrimos - we ran
- entendemos - we understand
- entendimos - we understood