What Has Been the Trend for the Average Age of First

What has been the trend for the average age of first marriages for males and females in the United States during the twentieth century?

A) The average age of first marriages has been increasing steadily since the twentieth century.
B) The average age of first marriages dropped until the '70s, after which it began rising again.
C) The average age of first marriages has been steadily decreasing since the twentieth century.
D) The average age of first marriages rose steadily until mid-century and has since been declining.