Is this a bad GRE question? Seems like the explanation is a kind of “story telling” and isnt relying on the information specific to the sentence. If they were expected to be admonished, wouldn’t something like “being admonished” as opposed to being punished (which nonplussed seems to correspond to if we take it to mean “not disconcerted, unperturbed (of a person)” in light of the second sentence saying “no surprise.” Seems like this would be a support between the two blanks.
update: for some reason my brain read “admonish” as meaning “absolve” 
