How Can the Increase in Female Labor Force Participation Over

How can the increase in female labor force participation over the last fifty years be explained?

A) There has been an increase in demand for clerical and service work.
B) Many women now postpone family formation to complete their education and establish themselves in the labor force.
C) A majority of women now work outside the home during their child-bearing years.
D) All of the above are true.
E) There has been no increase.