Building a mass transit system is likely to have which of the following effects?

a.) increasing air pollution
b.) traffic congestion
c.) increasing the temperature of the urban heat island
d.) none of the above

B.) traffic congestion
C.) increasing the temperature of the urban heat island

Building mass transit system would lower down the use of private vehicles. Therefore, it would most likely decrease the air pollution especially those that are emitted by vehicles. It would also lesser the traffic congestion and lastly, it may affect the temperature but the decrease of private transportation is most likely to have a better effect. Thus, the answer is letter D.