Answer:
The correct answer is: convergent evolution
Step-by-step explanation:
Convergent evolution is a type of evolution, in which analogous traits or analogous structures are formed in organisms that are not closely related, due to their exposure to similar environmental conditions.
It is a type of independent evolution in which the species of different ancestry evolve analogous traits or structures in order to adapt to similar environmental conditions.
Therefore, the presence of chitin in the cell walls of fungi and the exoskeletons of arthropods is most likely due to convergent evolution.