I was beginning to think that nouns that ended with "ão" such as "a televisão" and "a refeição" were feminine nouns, but then there's "Irmão" (brother) and "Irmã" (sister), so I guess that's not a reliable indication.
Correct, this isn't a rule.
Thank you for confirming.
Why it doesn't accept me "The boy eats on the floor"?
Not sure. Both "The boy eats on the ground" and "The boy eats on the floor" should be accepted. There must be some bug causing a problem with this sentence.
It seems to me that "...eats on the floor" is not incorrect. I think Duolingo neds to correct this.
Could this also be "eats off the floor"?
My guess: that would be do chão