Which of the Following Is Least Likely to Violate the Sherman

Which of the following is least likely to violate the Sherman Act or the Clayton Act?

A) Competitive firms A, B, and C meet and agree to charge a common price.
B) Competitive firms D and E, each with 35 percent market shares, merge into a single firm.
C) Competitive firms F and G independently charge lower prices to frequent customers than to occasional customers.
D) Large dominant firm H forces buyers to purchase its product X in order to buy its popular product Y.