You are at a restaurant where they offer both grass-fed and grain-fed beef, and are trying to decide which is the most sustainable choice. Which of the following statements is most logical?

Grain-fed beef is the most sustainable choice. These cattle have a high feed conversion rate, meaning it takes a lot of feed to produce a pound of meat, making it very nutritious.
Grain-fed beef is the most sustainable choice. Cows from feedlot operations are healthier because they are routinely given antibiotics.
Grass-fed beef is the most sustainable choice. These cattle are free to walk around and therefore they grow and gain weight much more rapidly than grain-fed feedlot animals, so you would get more value for your money.
Grass-fed beef is the most sustainable choice. Grass-fed beef represents a net gain for the human food supply because cows eat grasses that we can’t eat (from land that is typically unsuitable for human crops) and turn it into beef that we can eat.