Discover the Central Ideas of an Argument

Claim: Cheating exists because of incentive.

Levitt and Dubner support the claim with the reason: Sumo wrestlers who win eight or more matches earn a higher rank than those who do not.

Which evidence supports this reason?
A. A wrestler with ten victories would not throw a match because of the overall incentive to win.
B. The actual win percentage for 7-7 wrestlers is higher than the predicted win percentage.

What counterclaim might be made against the statistical evidence?
A. Sumo wrestling is an ancient tradition held sacred in Japan, so it cannot be corrupted.
B. There may be close ties between rival stables of sumo wrestlers.
C. A 7-7 wrestler might be more motivated to win and therefore perform better.
D. Wrestlers would not cheat because they want to win the $20,000 bonus prizes.