Excerpt from Conserving Energy and Preserving the Environment
Bureau of Transportation Statistics: US D. O.T.

2) Our communities, the economy and much of our lives are organized around our ability to travel easily and efficiently from home to work or school, to shop or play, to receive medical care or just for the sheer pleasure of traveling. This freedom has certain costs that accompany its many benefits. Vehicles, public and private, have to be purchased and operated; roads must be built and maintained; laws must be enforced so many people can travel at the same time; and hundreds of thousands of accidents inevitably occur.

3) The most fundamental costs of mobility, however, involve the energy required to move people and goods over any distance, and the pollution released as this energy is burned. As shown in Table 1, in 2000 Americans consumed more energy moving from place to place than industry used to produce all of its goods.
Which topic would be the BEST main idea for a new paragraph, that would be inserted between the current paragraphs 2 and 3?
A) the cost of those roads
B) the accessibility of certain roads
C) the speed limit on interstate roads
D) the safety measures provided for those roads