The correct option is B Extravagant
The words 'frugal' refers to being cautious and economical as regards to money or food.
Option A, stingy refers to being miserly or close-fisted.
Option B, extravagant refers to lacking restraint in spending money or using resources.
Option C, timid refers to showing a lack of courage and confidence.
Option D, frightening refers to making someone afraid or anxious.
Thus, according to the meaning, the word 'extravagant' is the farthest in meaning from the word 'frugal'.