The correct option is D Extravagant
The word 'thrifty' refers to using money and other resources carefully and not wastefully.
Option A, careless refers to showing a lack of attention.
Option B, instinctive refers to something done without conscious thought.
Option C, sentimental refers to being prompt by feelings of tenderness, sadness or nostalgia.
Option D, extravagant refers to a lack in restraint in spending money or resources.
Thus, according to the meaning, the word 'extravagant' is the most closest to the opposite of the word 'thrifty'.