​Which of the following is a violation of the antitrust laws?

A) ​A firm discussing/fixing price with its competitors
B) Making arrangements to stay out each other's markets
C) Merging with the competitor to eliminate competition
D) ​All of the above

All of the options violate antitrust laws. Discussing or fixing prices with competitors is price fixing, which colludes to set prices artificially high, and is a violation of antitrust laws. Making arrangements to stay out of each other's markets is market allocation, which allocates customers or territories between competitors, and is also a violation of antitrust laws. Merging with a competitor to eliminate competition reduces the number of firms in the market, leading to a decrease in competition, and is a violation of antitrust laws.