Answer:
The correct answer is C (The trait for shell thickening will not be selected by future mussel generations)
Step-by-step explanation:
The difference in thickness of shells is an advancement to adjust from the crabs and survive. Further clarification can be perused on the exploration directed by Aaren Freeman and James Byers.
It was found out that crabs discharge synthetic substances that are distinguished by mussels. Thus, mussels have a physical response activated by the synthetic substances which lead to the thickening of their shells.