Option 1: Horizon -> Refers to the line where earth and sky meet, not an opposite of zenith.
Option 2: Nadir -> The lowest point or weakest moment, directly opposite of zenith (highest point).
Option 3: Savage -> Means fierce or brutal, completely unrelated to zenith.
Option 4: Sober -> Means serious or not intoxicated, has no connection to zenith.
Hence, Option 2: Nadir -> Zenith means the highest point or peak, while nadir means the lowest point or bottom. They are perfect antonyms, representing opposite extremes of a vertical axis. -> correct