And there's a continuum from D to E as we increase the size of the key - a one-time pad is basically a key the size of the data. The bigger the key, the more possible brains an encrypted data set maps onto, and at some point it becomes quite likely that a happy brain is also contained within the possible brains.

But anyhow, I'd start caring less as early as B (for Nozick's Experience Machine reasons) - since my caring is on a continuum, it doesn't even raise any edge-case issues that the reality is on a continuum as well.