Option 1: prudent -> Means wise and sensible; fits perfectly as "expedient" means practical/advisable in the circumstances.
Option 2: alacritsous -> Not a valid English word (possibly a misspelling); cannot be a synonym.
Option 3: injudicious -> Means unwise or showing poor judgment; this is the opposite of "expedient."
Option 4: exorbitant -> Means excessively high or unreasonable (typically for prices); unrelated to the context of making a wise decision.
Hence, Option 1: prudent -> Both "expedient" and "prudent" convey that the manager made a wise, practical decision not to interfere since the intern was handling the situation skillfully. -> correct