Answer:
D.They carry human waste to treatment facilities away from cities.
Explanation:
Sewage system is a collection of systems that carries sewage (human waste) from the point it was produced to a place where it'll be treated or recycled. 
Since sewage is moved via the use of sewage system, it helps to fight the spread of disease by carrying human waste (sewage) to treatment facilities away from cities.
 
        
             
        
        
        
compacted and cemented together
brainliest please
 
        
             
        
        
        
A Multi-Celled organism has many cells (more than one). Examples would be plants, humans and animals/mammals. 
A Single-Celled organism only has one cell that makes up it's entire self. Examples would be bacteria and archaea. 
 
        
             
        
        
        
Answer:
it increases oxygen levels and decrease carbon dioxide levels
 
        
             
        
        
        
Answer:
multicellular; single celled organisms are often too tiny to be seen without a microscope