Let's talk about C. Take a look at line 20: "Any fair rule, then, would be better than no rule at all." This is in reference to the driving laws that the author discusses in paragraph two. The author clearly states that a fair rule is better than no rule. Answer choice C is basically a restatement of that quote. It even includes the exact driving rule that the author introduces, so we can be confident that the author would agree with C.
Here is the problem with D. Despite the discussion of the public's understanding and acceptance of these laws, the author does not indicate that the law itself is unnecessary. The agreement of people to be subject to this law is only what makes the law fair. It does not accomplish the same goal as the law itself, which is coordination.
Keep this in mind when you've narrowed it down to two answers. The answer with direct support is going to beat the answer that requires us to speculate. C has clear evidence in the passage. Even if you don't believe that the author would disagree with D, we don't have strong evidence that he/she would agree with it either. All we know is that the author never says the law itself is unnecessary. We don't have enough information, so we do not want to speculate. C is a stronger inference.