When Kann Et Al

When Kann et al. (1995) asked ninth- and twelfth-graders about their exercise habits, they found that

A) exercise rates for both boys and girls declined between ninth and twelfth grade.
B) exercise rates for both boys and girls increased between ninth and twelfth grade.
C) exercise rates for boys increased between ninth and twelfth grade while the rates for girls decreased.
D) exercise rates for girls increased between ninth and twelfth grade while the rates for boys decreased.