Taxi Drivers in Large Cities Are Likely to Earn More

Taxi drivers in large cities are likely to earn more than taxi drivers in rural areas. One reason for this wage differential could be that:

A) driving in large cities is more fun than driving in rural areas
B) driving in a large city is easier than driving in a rural area
C) it is unlikely that a taxi driver in a large city will be involved in a traffic accident that involves farm animals
D) driving a taxi in a large city is more dangerous than driving in a rural area