Option 1: Whinny -> refers to the soft cry or neigh of a horse, not related to wasteful behavior.
Option 2: Binge -> means to indulge excessively in an activity, but doesn't capture the wasteful aspect of squander.
Option 3: Waste -> means to use carelessly or extravagantly, directly synonymous with squander.
Option 4: Whimsy -> refers to playful or fanciful behavior, unrelated to the meaning of squander.
Hence, Option 3: Waste -> "Squander" means to waste resources (money, time, opportunities) in a reckless or foolish manner, making "waste" the most accurate synonym among the given options -> correct