Which of the following best explains why productivity growth in the United States has been faster than in other leading industrialized nations? A) There are fewer government regulations in the United States regarding the way firms can hire and fire workers. B) The financial systems of foreign countries are generally more efficient than those in the United States. C) European countries have more flexible policies regarding the number of hours employees are permitted to work. D) Job mobility in the United States is more restricted than it is in many foreign countries.