Which of the following are valid conclusions from the data on graph 2? Check all that apply.
a) A kilogram of cheese results in lower greenhouse gas emissions than a kilogram of pork.
b) Pork's post-farmgate emissions are higher than cheese's post-farmgate emissions.
c) Lamb meat's overall contribution to global warming is greater than beef's overall contribution.
d) Chicken and tuna produce the lowest greenhouse gas emissions, per kilogram of food, of all meats.