If You Pick Up a Package at the Grocery Store

If you pick up a package at the grocery store and it says "grass-fed beef," what does that mean?

A) The cows in the CAFOs were fed grass instead of grain.
B) The cows have adapted, through several generations at the same farm, to digest grass instead of grain.
C) The cows are allowed to roam free and graze on pasture lands.
D) The cows eat grass and quickly gain weight, making the meat very tender.
E) Since they are grass-fed, the cows have also been given high amounts of antibiotics.