PT86.S1.Q21 - Farming with artificial fertilizers...

Hi all! I am reviewing PT86.S1.Q21. I understand why we can get rid of answer choices a,c and e as well as the general flaw in the argument being that the spread of organic farming is only a problem for having enough food if all farmers switch to organic farming. However, I am having trouble with what differentiates answers b and d. I know it has something to do with the logical meaning of some and all, and their opposites not some and not all. The explanation video for this question leaves it up to us to think about at the end, but I'm hitting a wall so all help appreciated! Thanks!