Consider the following choices. which one of the following choices is correct? a. recessions lasted for a shorter period of time in the first half of the twentieth century than in the second half. b. expansions have become shorter in the second half of the twentieth century compared to the first half. c. recessions were more severe and lasted longer in the first half of the twentieth century and became shorter and milder in the second half. d. both expansions and recession last for about the same period of time in the second half of the twentieth century.