During World War I, women in the United States played a significant role in various ways. The most notable contributions include:
D. They often took the jobs vacated by men who were off fighting in the war.
As men left for military service, women stepped into roles in factories, offices, and other sectors previously dominated by men, which helped sustain the war economy.
B. They became unified to win the right of suffrage.
The women's suffrage movement gained momentum during this period, with many women advocating for their right to vote, arguing that their contributions to the war effort deserved recognition through suffrage.
While options A and C do not accurately reflect the primary roles women played during this specific time, option D and option B are notable aspects of their involvement. However, if you are looking for the most significant role they played in a direct sense related to the war, the best answer would be D.