Answer:
Explanation:
Oxygen is of no use to them, so they release it into the air. So there's a simple explanation for the Great Oxidation Event. It was the cyanobacteria, pumping out unwanted oxygen, that transformed Earth's atmosphere.
 
        
                    
             
        
        
        
Answer:
immigration help to a country to grow their labor or taxes 
Explanation:
Immigrants also make an important contribution to the U.S. economy. Most directly, immigration increases potential economic output by increasing the size of the labor force. Immigrants also contribute to increasing productivity. 
 
        
             
        
        
        
Geographers use the regional unit to map features of particular interest, and data can be compared between regions to help understand trends, identify patterns, or assist in explaining a particular phenomenon. Regions are traditionally defined by internal characteristics that provide a sense of place.