The use of automobile safety seats by children aged 4 and under has nearly doubled in the past 8 years. It is clear that this increase has prevented child fatalities that otherwise would have occurred, because although the number of children aged 4 and under who were killed while riding in cars involved in accidents rose 10 percent over the past 8 years, the total number of serious automobile accidents
rose by 20 percent during that period.
Which one of the following, if true, most strengthens the argument?
(A) Some of the automobile safety seats purchased for children under 4 continue to be used after the child reaches the age of 5.
(B) The proportion of serious automobile accidents involving child passengers has remained constant over the past 8 years.
(C) Children are taking more trips in cars today than they were 8 years ago, but the average total time they spend in cars has remained constant.
(D) The sharpest increase in the use of automobile safety seats over the past 8 years has been for children over the age of 2.
(E) The number of fatalities among adults involved in automobile accidents rose by 10 percent over the past 8 years.
The first thing I thought when I read the bolded part of the argument was, "The total number of serious automobile accidents does not specify the age of the people in the cars - what if that 20% increase was made up entirely of adults?" If that were true, then the argument that the increase in child fatalities is irrelevant would be false. So, if you want to strengthen the claim, look for a piece of information stating that the number of children in these accidents has increased as well. Answer (B) states exactly that - since the
of accidents involving children has remained constant, then any increase in ALL accidents means there's an increase in the RELEVANT accidents we care about. (B) is the answer.