In this task, you are given a question and answer for that. The answer will fill in the blank or will complete the unfinished question. Your task is to provide an explanation based on the given question or fill-in-the-blank statement, and answer.

Question: Mona lives in a nation that uses a lot of fossil fuels. What would happen to her countries levels of air pollution if they were to decrease their usage? 
 Answer: decrease
Because richer nations use more fossil fuels, they also cause more air pollution and global warming than poorer nations do.

Question: Ron watches a wave for 10 seconds and notices 10 crests. He watches another wave for 10 seconds and sees 5 crests. Which wave has a greater frequency? 
 Answer: 10 crests
Wave frequency can be measured by counting the number of crests or compressions that pass the point in 1 second or other time period. The higher the number is, the greater is the frequency of the wave.

Question: When people figured out how to grow food the levels of food in the world 
 Answer: increased

Better farming techniques and machines increased the food supply and the distribution of food.