I believe the answer can be C, correct me if i’m wrong
        
                    
             
        
        
        
Answer:
Walking
Explanation:
A muscle cell usually contracts or expands simultaneously when one is working or doing some activities like running, exercises, house chores e.t.c
Muscles are flexible fibers that are very essential appendages for locomotion in human beings. 
For muscle cells to contract, they are pulled together thereby causing tension in the muscle. When they are relaxed, they move away from one another. 
 
        
             
        
        
        
Electromagnet. 85% sure on this. Let me know if I'm right.
        
             
        
        
        
Symbiotic relationship is the relationship that the organisms in the ecosystem have. This is their way of interaction. Every organism has different interaction with the other. Based on the organisms given above which are the pistol shrimp and the gobies, being dependent on each other for shelter and protection shows the relationship of mutualism. This means that both benefit on each other.