Final answer:
The period referred to when Mary Pickford was popular, and the flapper girl mystique was popularized, is the Roaring Twenties, also known as the Jazz Age. This era, particularly the early 1920s, was known for its significant cultural and social changes, especially in regard to women's rights and freedoms.
Step-by-step explanation:
The period being referred to in the question is A) The Roaring Twenties. During this era, the silent movies of the early 1920s saw the rise of cinema's first generation of stars, one of whom was Mary Pickford, affectionately known as America's Sweetheart. She, along with others like Clara Bow and Charlie Chaplin, had a significant influence on the public. The flapper girl image that Mary Pickford helped popularize was the embodiment of the modern and liberated woman of the Jazz Age, which was characterized by shorter hairstyles, shorter skirts, and a more permissive attitude towards social and sexual norms.
This era was also marked by significant gains in women's rights, including the ratification of the Nineteenth Amendment, guaranteeing women full voting rights. The flapper lifestyle was a symbol of the social freedom women were beginning to enjoy after the repressive Victorian era norms. This generation of women expressed their newfound liberation through dance, fashion, and other forms of social expression. The Renaissance, Victorian Era, and Great Depression were other historical periods that did not embody the flapper or the mass appeal of movie stars like Mary Pickford.