Recently, highly skilled workers in Eastern Europe have left jobs in record numbers to emigrate to the West. It is ttherefore likely that skilled workers who remain in Eastern Europe are in high demand in their home countries. Which one of the following, if true, most seriously weakens the argument? ['Eastern European factories prefer to hire workers from their home countries rather than to import workers from abroad.', 'Because of the departure of skilled workers from Eastern European countries, many positions are now unfilled.', 'Major changes in Eastern European economic structures have led to the elimination of many positions previously held by the highly skilled emigrants.', 'Eastern European countries plan to train many new workers to replace the highly skilled workers who have emigrated.']