The sentences in this section are confusing. They all sound like they could mean something other than their literal meaning but do they? Could this sentence be used as a present tense version of they way we say in English "what's come over him"? As in why has he such a change in mood/behaviour?
Because prepositions don’t typically match exactly in all of their meanings between languages, they often have more than one translation into another language. This meaning of the English phrasal verb “come over” would be translated by buail or tar ar, e.g. Cad a bhuail é? or Cad a tháinig air? ; this exercise doesn’t have that meaning.