Answer:
Option D The Clayton Act.
Explanation:
This legislation says that the unethical business practices are forbidden. This means if the Nitro dealer is asking for $500 extra for no reason then he is following an unethical business practice. So the Nitro Dealer is violating Clayton Antitrust act by fixing a price and then enforcing Sandra for purchase. So the violation is of provision of Clayton Act which prohibits price fixing.