555 - Logical Reasoning

There is clear evidence that the mandated use of safety seats by children under age four has resulted in fewer child fatalities over the past five years. Compared to the five-year period prior to the passage of laws requiring the use of safety seats, fatalities of children under age four have decreased by 30 percent.
Which one of the following, if true, most substantially strengthens the argument above?

1. The number of serious automobile accidents involving children under age four has remained steady over the past five years.
2. Automobile accidents involving children have decreased sharply over the past five years.
3. The use of air bags in automobiles has increased by 30 percent over the past five years.
4. Most fatal automobile accidents involving children under age four occur in the driveway of their home.
5. The number of teenage drivers has increased by 30 percent over the past five years.