Think about it, for the first one, blood is primarily made up of water. dehydration is the lack of water. lower volume of water in the body=lower blood volume.
second one, low blood pressure 
third one, not sure... sorry
        
                    
             
        
        
        
The integumentary system, the skin, protects the internal organs from harmful bacteria, sunlight, and injury. The skin is the largest organ of the body and consists of two layers: the epidermis and the dermis. The epidermis is the outer layer. It is made up of dead cells and new cells which make the body waterproof, give color to the skin, and help maintain the body's hydration levels.
 
        
                    
             
        
        
        
Answer:
I think it's all of them.