@EmilyMarieMenendez since this is a Necessary Assumption question, we are looking for the assumption that if FALSE makes the conclusion INVALID.
So let's pretend B was FALSE. In other words, let's pretend that patients' predictions of sudden changes in their medical status are equally likely to be remembered by medical staff whether or not the change actually occurs. In that case, it would be invalid to say the case is "analogous" to the case where maternity room staff were MORE likely to remember busy nights with full moons than busy nights without full moons. We can't compare cases (i.e. consider them analogous) when one case involves two equally likely scenarios and the other case involves two scenarios with unequal likelihoods.
Therefore, (B) must be TRUE, in other words, it is a necessary assumption of the argument. I hope that helps!
