Answer:
i really dont know but i did try to help u
Explanation:
 
        
             
        
        
        
It form the contraction and relaxation of muscle
        
             
        
        
        
Answer:
The bones are homologous structures 
Explanation:
Homologous structures are the structure which are found similar in appearance in different organisms. 
The homologous structures in different organism shows that they shared a common ancestor or they diverged from a common ancestor during course of evolution that is these homologous structures are the result of the divergent evolution.
In the given question, the bat, dolphin and the cat shows the same structure of bone which indicates that they have evolved from a common ancestor and is true as they all belong to mammals.
Thus, the bones are homologous structures is correct.