Option 1: Austere -> means severe, strict, or simple in manner; unrelated to movement or quickness.
Option 2: Agile -> means quick and easy in movement, mentally sharp; directly synonymous with nimble.
Option 3: Languid -> means slow, relaxed, lacking energy; opposite of nimble.
Option 4: Lazy -> means unwilling to work or move; antonym of nimble.
Hence, Option 2: Agile -> Both "nimble" and "agile" describe someone or something that moves quickly, lightly, and with ease, making them perfect synonyms -> correct