The correct answer is Option A.
GARISH means LOUD, GAUDY and SHOWY. The antonym of the word will be the word which will mean the opposite.
TASTEFUL means something that shows good aesthetic taste, attractive, pleasing and something that is not over bright and gaudy.
Thus Option A is the correct answer.
The remaining options are incorrect because:
GREEN means aplenty of nature.
SCENIC means picturesque and impressive natural scenery.
CONTRASTING means differ strikingly.