Option 1 -> Suggests lack of interest or concern, similar to a mechanical, routine action done without genuine feeling.
Option 2 -> Implies eager and intense interest, which is the opposite of a routine, unenthusiastic gesture.
Option 3 -> Indicates a bright, warm, radiant smile showing genuine happiness, contrary to a cursory acknowledgment.
Option 4 -> Conveys unfriendliness or opposition, whereas perfunctory is neutral rather than antagonistic.
Hence, Option 1: indifferent -> "Perfunctory" means done as a matter of routine or duty without real interest, attention, or feeling - essentially mechanical and superficial. An indifferent smile similarly lacks warmth and genuine engagement, making it the closest match. -> correct