The correct answer is formal.
The adjective that best describes Lincoln’s diction in the B) Gettysburg address is formal.
Abraham Lincoln gave the famous speech in Gettysburg in a formal way to mark the importance to the occasion. The speech was at the dedication of the battlefield cemetery was eloquent, emotive and clear. Abraham Lincoln delivered the Gettysburg speech after the deadly battle in that region. The vision that Lincoln describes as a conclusion of his speech was of a nation living in peace and freedom.