D. w. griffith's the birth of a nation (1915) was extremely controversial because: question 1 options:
a) it required the use of a full orchestra, which cost too much money for most of the exhibitors
b) it was 3 hours long and exhibitors knew their patrons could not sit still for that long
c) it used flashbacks and other new editing conventions that were confusing to contemporary audiences
d) its racist account of the role of african-americans in the post-civil war south

D) Its racist account of the role of African-Americans in the post-Civil War South

Explanation:

In the Birth of a Nation, African Americans were racistly depcited as aggresive, brute, and the Ku Kux Klan was shown as a good force that tried to protect white people, and especially, white women, from black men.

This racist depictions made the film very polemic, so much that there are film historians who have argued that the Birth of a Nation is the most polemic film in the history of the United States.

African Americans around the country protested the film's exhibition, especially in Boston, and many other progressively-minded people did the same. These efforts were fruitless, probably because the First Amendment protects freedom of speech to a great extent.

However, these efforts did inspire D.W. Griffith to make another film years later, called "Intolerance".