Official Solution:
There are several renowned Athletics clubs in the city of Sportsville. It is a common practice in Sportsville that the athletes change clubs frequently, some every year. This year several sprinters have left the club Acerunners. However the manager of Acerunners claims that not only is the number of sprinters joining the club this year higher than those leaving, but also is the average speed of the athletes who joined higher than the average speed of all the sprinters of the club. Therefore it can be concluded that the average speed of the sprinters at Acerunners has risen this year.
Which of the following statements most strongly strengthens the above conclusion?
A. The average speed of the sprinters in Sportsville is lower than those of the adjacent city.
B. This year many athletes leaving Acerunners retired from Athletics permanently.
C. The average speed of all the sprinters at Acerunners this year is the highest among all the clubs in Sportsville.
D. The sprinters who left Acerunners were on an average slower than the sprinters of Acerunners.
E. Some new marathon runners whose average speed is higher than that of all the marathon runners of Acerunners joined the club this year.
The passage by itself does not lead to the conclusion that the average speed of all the sprinters has risen this year, since the passage provides information only about the sprinters who joined the club, but not those who left. In order to arrive at the conclusion, it must be established that the average speed of the sprinters joining the club is higher than the average speed of the sprinters leaving the club.
A. The comparison made in the argument is between the average speed of sprinters in Acerunners last year and that this year. The argument has nothing to do with the overall average speed of sprinters of Sportsville. Hence this option is irrelevant.
B. For what purpose the sprinters left Acerunners has no bearing on the change in average speed of the sprinters in Acerunners.
C. The comparison made in the argument is between the average speed of sprinters in Acerunners last year and that this year. The argument has nothing to do with the comparison between average speed of sprinters or Acerunners and that of other clubs. Hence this option is irrelevant.
D. CORRECT. If the sprinters who left have a lower speed than average and (as given in the passage) the sprinters who joined have a higher speed than average, then it can be concluded that the average speed of all the sprinters at Acerunners increased.
E. The argument is about sprinters, not marathon runners. Hence this option is not relevant.
Answer: D