An Historical Study (Twenge,2001)on the Effects of Changes in Women's

An historical study (Twenge,2001) on the effects of changes in women's social roles in the United States during the twentieth century showed that

A) both the opportunities for women and women's assertiveness steadily increased over the century.
B) the opportunities for women increased,but women's assertiveness stayed steady over the century.
C) the opportunities for women increased,but women's assertiveness decreased over the century.
D) both opportunities for women and women's assertiveness went up and down in tandem over the century.