Final answer:
Lincoln's choice to begin the Gettysburg Address with 'Four score and seven years ago' is especially effective because it creates a sense of historical significance, captures attention with a unique opening, and establishes a formal tone.
Step-by-step explanation:
Lincoln's choice to begin the Gettysburg Address with 'Four score and seven years ago' is especially effective because it creates a sense of historical significance, captures attention with a unique opening, and establishes a formal tone. By using this phrase, Lincoln immediately transports the audience back in time to the founding of the nation, emphasizing the importance of the events being discussed. This opening also grabs the attention of the listeners and sets the stage for the rest of the speech.