B: The data collection method used was nonrandom since the athletes using Fastex shoes may have trained better.
This is false because they followed the same nutrition plan and training program during the study.
C. The data collection method used was unfair since the athletes given Fastex shoes may have been better runners than the athletes given SportsPlus shoes.
This is also false because members of both groups were pretested and determined to have equal athletic ability
D. Each group used one shoe design.
So, the correct option is A