Answer:
B) Americans value their mobility.
Step-by-step explanation:
Mobility and its cost is the main concepts being talked about throughout the paragraph. The last part of the paragraph talks about the costs, we have to pay to afford this freedom of mobility. More over when we value something, we usually have to pay some cost. So starting the paragraph with "Americans value their mobility.", will be good start to let the readers know what is about to come in next lines.
A) Americans value freedom, will be very misleading, because it is freedom of mobility, not freedom in its conventional sense, which the paragraph/author is talking about.
C) Americans are the victims of progress will also be a bad start because, reader will infer that next few lines will try to prove that progress is bad for Americans.
D) Americans are able to afford large vehicles, would also be a misleading start because this does not signify the importance and cost of mobility.