逻辑单题10：
Although the percentage of first graders in Almaria who were excellent readers varied little between 1995 and 2010, the percentage of first graders who had considerable difficulty reading their schoolbooks increased markedly during that period. This evidence strongly indicates that the average reading ability of first graders decreased between 1995 and 2010.
10. Which of the following, if true, provides the strongest additional support for the argument?
A. The number of hours devoted to reading activities in first-grade classrooms in Almaria did not vary significantly, on average, between 1995 and 2010.
B. The percentage of first graders in Almaria who had difficulty solving arithmetic problems did not increase as much between 1995 and 2010 as did the percentage of first graders who had reading difficulties.
C. The number of children in Almaria who were enrolled as first graders decreased steadily between 1995 and 2010.
D. The average difficulty of the schoolbooks used in first-grade classrooms in Almaria decreased between 1995 and 2010.
E. The average number of schoolbooks used in first-grade classrooms in Almaria increased between 1995 and 2010.
答案：D