United States politician: Although the amount of United States goods shipped to Mexico doubled in the year after tariffs on trade between the two countries were reduced, it does not follow that the reduction in tariffs caused the sales of United States goods to companies and consumers in Mexico to double that year, because __ Which of the following, if true, most logically completes the politician's argument? ['many of the United States companies that produced goods that year had competitors based in Mexico that had long produced the same kind of goods', 'there was no significant change in the employment rate in either of the countries that year', "most of the increase in goods shipped by United States companies to Mexico was in parts shipped to the companies' newly relocated subsidiaries for assembly and subsequent shipment back to the United States", 'the amount of Mexican goods shipped to the United States remained the same as it had been before the tariff reductions']