Which of the following sentences would most effectively introduce the subject of this paragraph and act as a transition from the preceding paragraph?
F. Film animation began as a series of pictures that simulated motion when shown together rapidly.
G. Flip-books were a popular ‘toy’ in the 1950s.
H. Some graphic artists have no interest in creating motion pictures and are  focusing instead on print media, such as that used in advertising.
J. Film animation has changed dramatically over the past several decades.