Hormones because if you think about it. Vertebrates must have backbones and mammals have them. And, humans are basically mammals. And the glands secrete hormones.
        
             
        
        
        
with this option given I don't think there is an odd one
 
        
                    
             
        
        
        
Answer:
A 
Explanation:
Fertilizations occurs in the fallopian tube. 
Point "a" is located where the fallopian tube is at
Hence, fertilization is most likely to occur at point A 
 
        
                    
             
        
        
        
Answer:A
Explanation:
It absorbs carbon dioxide