A forest range office notes that the eastern beat's share of the fire reports reaching the range fell from a third to a fifth over four years, and the range officer concludes that fires in the eastern beat have grown fewer. Which of the following, if true, most seriously undermines that conclusion?

A share can shrink while the thing it is a share of grows. A third of 120 is 40 reports; a fifth of 400 is 80, so the eastern beat's fires have doubled while its share fell. The officer has read a smaller slice of a much larger cake as less cake. The beat's size, the printed form and the two extra guards say nothing about how many fires there were in either year.