The Construct of Middle-Age Emerged When

The construct of middle-age emerged when

A) a more educated workforce continued working longer.
B) increased consumerism in the early 20th Century created a desire for greater wealth.
C) the loss of healthy young men during World Wars I and II created an excess of healthy, marriageable young women.
D) 20th-century parents began to bear fewer children and live long enough to see their children grow up and leave home.