Which two factors make regulating mergers​ complicated? A. ​First, firms may lobby government officials to influence their decision to approve the merger.​ Second, by the time the government officials reach a decision regarding the​ merger, the firms often decide not to merge. B. ​First, the time it takes to reach a decision to approve a merger is so long that the firms often have new owners and mangers.​ Second, by​ law, government officials are not allowed to consider the impact of foreign trade​ (exports and​ imports) on the degree of competition in the markets of the merged firms. C. ​First, the Federal Trade Commission and the Antitrust Division of the U. S. Department of Justice must both approve mergers.​ Second, the concentration ratios that are used to evaluate the degree of competition the merged firms face are flawed. D. ​First, it is not always clear what market firms are in.​ Second, the newly merged firm might be more efficient than the merging firms were individually.