Final answer:
The flu pandemic and the women's liberation movement did not trigger a rapid increase in UN membership.
Step-by-step explanation:
The United Nations was created after World War II, and several events triggered a rapid increase in UN membership. However, the flu pandemic and the women's liberation movement were not events that directly led to an increase in UN membership.
The flu pandemic was a global health crisis that affected many countries, but it did not have a direct impact on the formation or expansion of the United Nations. Similarly, the women's liberation movement was a social and political movement advocating for women's rights, but it did not trigger a rapid increase in UN membership.