A very good question D
According to me answer is d we have strengthen the argument so option C gives us a fact that most of their time idling , so parking will be very good to reduce the emission of exhaust as the buses will get parking space they will be turned of , thus reducing exhaust.
According to me answer is d we have strengthen the argument so option C gives us a fact that most of their time idling , so parking will be very good to reduce the emission of exhaust as the buses will get parking space they will be turned of , thus reducing exhaust.



.jpg)



