Help me with this GRE question

Solution 1:

One problem with

Human nature and long distances have made exceeding the speed limit a controversial habit in the state, so the legislators surprised no one when, acceding to public demand, they endorsed increased penalties for speeding

is that it is not clear how human nature and long distances could be at the root of a controversial habit. Long distances might make speeding a habit, but what makes it controversial? Neither of those two factors seem to make for controversy.

Another problem is that having the legislators endorse greater penalties would not be a natural expectation caused by the controversial habit. If there was controversy over whether speeding was a problem or not, there would not be clear public demand for the legislators to accede to, and it would not be a foregone conclusion that the politicians would endorse higher penalties for it.

Solution 2:

It would make sense grammatically but it wouldn't make sense when you consider causality — as mgkrebbs pointed out; the legislation should be a function of public demand — choosing A would make the causal choice of D ambiguous (and therefore the qualifier "surprised no one" wouldn't make any sense).