Answer:
D. Grew slowly, due to slow growth of the output of goods and services per hour of U.S. workers' time during those decades.
Step-by-step explanation:
According to mainstream economic theory, real wages depend on the marginal productivity of labor (the amount of extra output produced by each additional worker). In other words, in theory, wages, and correspondingly, household income, depend on labor productivity.
During the 1970s and 1980s, labor productivity was relatively stagnant. High inflation, slow technological change, and deindustrialization have been proposed as explanations for this event.
The slowdown of labor productivity ended in the 1990s, with the arrival of information technology.