The problem with (B) is that the "veil of ignorance" is a hypothetical situation. No one has ever claimed that it is actually possible to create a real veil of ignorance. We can still learn valuable lessons from hypotheticals, even if we can't actualize them. This is why (B) is wrong.
If (C), on the other hand, is correct, then we can immediately apply it to the cake example to see how it undermines the claim in 49-51. If people are willing to risk one primary good (calling cake here a primary good), then a person might cut it unequally and hope that they get the larger piece. Hope this helps!
