Answer:
elderly, specifically 50-74.
Explanation:
According to macmillan.org, the risk for cancer increases with age.
https://www.macmillan.org.uk/information-and-support/...cancer/what-is-cancer.html
If we are to go off of percentages, I would say a higher percent of children (per capita) get chemo, as it is a lot harder to say, "oh well i will die soon anyways" with a child.
 
        
             
        
        
        
Answer: salt
Freshwater is defined as having a low salt concentration, usually less than 1%.
Explanation:
Freshwater refers to the bodies of water that contain very low levels of dissolved salts. So, freshwater are unique for their low salt content (about 0.5% of salt) compared to the sea water with high salt content.
Examples of freshwater include rivers and spring
 
        
                    
             
        
        
        
Answer: After several days, a large bubble of gas collected in the upside-down beaker contains OXYGEN.
Explanation: 
Plants are known to be be autotrophic (producers) through the use of inorganic substance such as water, carbondioxide and light energy from sunlight in a process known as photosynthesis. 
An experiment was carried out by Latecia for investigation of the gas production of a water plant. It's therefore expected that OXYGEN gas which is the by-product given off during photosynthesis in green plants would be collected from the upside down beaker as gas bubbles.