Business cycles are
a. all roughly the same in duration and severity.
b. alternating periods of smoothly expanding and contracting economic activity, which are usually illustrated using movements in nominal gdp.
c. alternating periods of expanding and contracting economic activity, which are usually illustrated using movements in real gdp.
d. alternating periods in which real gdp increases in an expansion to a business cycle trough and then decreases in a recession to a business cycle peak.
