It also seems hard to me that for some reason when it was a new word I never learned before, I could usually roll my mouse over the word and it'll tell me because I never used that word, it doesn't do that anymore and I find it a little unfair for new Spanish learners.
There is a school of thought that if you get it wrong first sometimes, it strengthens the learning process. Keep Positive! I find that if I get the answer too easily, I forget it quickly too. Just accept the mistake, even yippee it,then move on. Learning is fun unless you let it get you down
labordea, as I've said before, the lack of context for this short sentences makes it difficult, but some situations I can think of to specify cow meat is when you make a comparison or a choice, I don´t know what lesson were you learning. Sorry for not being as helpful as I wish.
The same for any noun: "el" is for masculine nouns and "la" is for feminine nouns. Remember: in spanish, ALL nouns are either masculine or feminine. There is no rule to find out whether a noun is masculine or feminine. You must remember each word and its gender (for example, carne is feminine and pollo is masculine).