Answer:
homologous structures.
Step-by-step explanation:
This evidence of evolution is an example of homologous structures. Homologous structures are structures in different species that have a similar underlying structure and are thought to have evolved from a common ancestor. In this case, the scientist is observing that the bones in the monkey arm and the bat wing are similar, but with variations in their characteristics. This suggests that these structures evolved from a common ancestor, providing evidence for the theory of evolution.