An organic shape is typically irregular and follows the forms found in nature. Based on the options you provided:
a. an egg shape - this is an organic shape.
b. a wavy shape - this is also an organic shape.
c. an octagon - this is a geometric shape.
d. a cube shape - this is also a geometric shape.
Both a. an egg shape and b. a wavy shape are considered organic shapes. If you need to choose one, either would be correct, but the egg shape is more commonly recognized as organic.