Whitehall found that senior administrators had worse health than the permanent secretaries above them - not merely that the lowest grade did worst of all. Why does a step at every rung, rather than a cliff at the bottom, change what you can conclude?

B. Because a step at every rung points to relative standing.

A cliff and a gradient accuse different suspects. Deprivation stops mattering above a line; rank does not, and these were civil servants, all employed, all housed, all covered by the same health service. That is what forces the explanation toward control, security and where you stand relative to the person above you.