C I know this is hard but it’s easy
 
        
             
        
        
        
Answer:
Transport oxygen.
Explanation:
Red blood cells transport oxygen throughout the body with the help of hemoglobin.
 
        
             
        
        
        
Answer:
390W are used to just power the leaf blower. 
Explanation:
Therefor less than half its power is being used for it to actually do its job.
Hope that helps! Good luck!
 
        
             
        
        
        
If want  a direct answer it would be the decrease in mice, but if you want to get technical the decrease in grain spills caused mice to leave so that would be the indirect cause
        
                    
             
        
        
        
Superior vena cava- upper body inferior vena cava
lower body- bother drain into the right atrium