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Can someone tell me what's the difference between choice D) and E) ? To me, both choices bring up the reason that people are not obeying the new seat belt law and that is why the traffic deaths remained the same. Thanks

D gives us a reason why the seat belt laws may not have been effective. If they're not enforced, that's likely to decrease their effectiveness.

E doesn't do anything to explain why this particular city did not see a decline in traffic fatalities after the enactment of seat belt laws. E does mention that not everyone is following the seat belt laws, but it doesn't explain WHY people aren't following them (or why there hasn't been a decline in fatalities since the enactment of the laws.