The part that does not belong to carpel is
filament
The correct option is D.
Explanation for correct option-
Explanation for incorrect options-
Option A:
Stigma is incorrect because it is the topmost sticky part of the carpel where the pollen grains land.
Option B:
Style is incorrect because it is the thin elongated stalk-like structure of the carpel. It connects the stigma and the ovary.
Option C:
The ovary is incorrect because it is the lowermost bulged part of the carpel that holds the ovules.
Therefore the part that does not belong to the carpel is the filament.