Answer:
B. Culture A will gain one custom, and Culture B will remain relatively unchanged.
Step-by-step explanation:
Cultural appropriation is the adoption of one or multiple elements of one culture by members of another culture. On its own, this phenomenon is not problematic, but the controversy can arise when members of a dominant culture take customs from the members of an oppressed culture.
If Culture A appropriates a custom of Culture B, Culture A will gain one new custom, while Culture B will remain relatively unchanged.