Option 1 -> Intelligent is a synonym of sagacious, not an antonym.
Option 2 -> Unwise is the direct opposite of sagacious, which means wise and showing good judgment.
Option 3 -> Perspicacious is a synonym meaning having keen insight or understanding.
Option 4 -> Expensive relates to cost and has no connection to sagacious.
Hence, Option 2: Unwise -> Sagacious means wise, shrewd, and showing sound judgment, so its opposite would be unwise or foolish -> correct