The answer is a. This question tests basic knowledge about air pollution, and is study guide question 44. The answer is d. The answer is a rewritten version of study guide question 8. In this question, one point was given for demonstrating what causes each of the four steps of the water cycle to occur, and two points were given for linking the change in each step to an increase in city size and amount.
Evaporation changes liquid water to water vapor.
Paving an area will increase the temperature of the region and stop the liquid water from soaking in, causing more of the water to evaporate into the atmosphere. Also, increases in water use such as fountains in parks, watering the lawn, and building swimming pools will cause more evaporation. An increase in vehicle traffic will also cause evaporation since water vapor is created when fossil fuels are discharged. Many people described the use of cooling towers or the building of dams, but larger cities do not require mor industry or dams, so you had to explicitly describe why a dam would be needed for a city to receive credit. Particles will increase in cities due to larger amounts of traffic which discharge particles from their vehicle exhaust or construction of new housing developments and roads which encourage soil erosion.