It asked me about "repas" meaning meal, a word it hasn't taught me yet. I think they should ensure that a word has been introduced to us, before asking us about it! Luckily in this particular case, I already knew the word repas means meal.
If meal was plural, mon would be come "mes" to indicate this. For example "my friend" is "mon ami", but "my friends" is "mes amis". So for it to be "my meals? a tomato." the french would be "mes repas? Une tomate"