Why is E incorrect?

I have the same question. Why would the fact that some farmland can only support animal farming weaken the moral argument for eating meat? I also got E

I chose E as well

I would argue against E on the grounds that morally permissible and good for human health are not the same thing. This is an argument about what is moral, not what is healthy. Furthermore, the author is not arguing for only eating grain- there are other options between grain and meat, like veg, dairy, and legumes