Answer: (D).
According to the real business cycle, "changes in the level of technology are the main causes of inflation and fluctuations in real GDP".
Step-by-step explanation:
The "real business cycle" states that an economy during its lifetime will go through all the various stages of a business cycle which include; expansion, peak, recession, depression, trough and recovery. There will be periods where economic activities will be high and other periods when they will be low.
According to the real business cycle, technological innovation or shocks, which determine the extent to which inputs are converted to outputs, are responsible for the changes in the economy (such as inflation and real GDP fluctuations).