Transportation has been made much easier thanks to the invention of cars. However, cars are the greatest contributor of air pollution.
A. The invention of cars has made transportation much easier, but cars are among the greatest contributors of air pollution.
B. However easier the invention of cars has made transportation, it is cars that are among the greatest contributors of air pollution.
C. Although the invention of cars has made transportation much easier, cars are the greatest contributor of air pollution.
D. Although the invention of cars has made transportation much easier, people use cars to contribute to the pollution of air.