Since the oil crisis of 1973, the American job sector that has greatly increased is "D. Low-wage service work." This period saw a shift in the U.S. economy towards the service sector, which includes jobs in retail, hospitality, healthcare support, and other service-related industries. Many of these jobs are characterized by lower wages compared to traditional manufacturing jobs, which declined during this time. The service sector's growth has been a notable trend in the U.S. labor market over the decades following the oil crisis.