Answer:
By not having more offspring.
Explanation:
There are many ways of reaching a zero population growth, but some of them are 0% ethical. But, if the population stops having offspring, there won't be a population growth, instead, the population will decrease in number. 
- In 2017 the country with the biggest population was China, and the country with the biggest population growth in that same year was South Sudan, with a 3,83% population growth, according to statista and IndexMundi 
- Currently, in 2019, China still is the country with the biggest population, and, as for the highest population growth this year, we will only be able to say with 100% certainty when the year ends. 
Hope it helped,
BiologiaMagister
 
        
             
        
        
        
Answer:
Fermentation
Explanation:
I think there is a typo in the question as it doesn't make sense to breakdown oxygen - do you mean the proces of breaking down sugar?
Fermentation vis a type of anaerobic respiration, meaning it occurs in the absence of oxygen. It occurs when sugar is broken down into ethanol and carbon dioxide. It is used to produce alcoholic drinks like beer and wine, and in the production of bread. 
 
        
             
        
        
        
the breakdown of food molecules
        
                    
             
        
        
        
answer:
that is very cool, and thanks for the points
explanation:
- that's all i had to say :)