Answer: The correct answer for the blank is-
D. Ukraine.
Ukraine has one of the most amazing and iconic culture of making decorated Easter eggs ( also called pysanky).
The term pysanky is derived from 'pysaty' , which means to write.
Ukraine is famous at international level for decorating eggs with vibrant, colorful designs by making use of geometrical ( such as triangles) and symbolic patterns.
Thus, option D) is the right answer.