Which of the following correctly explains how selective incorporation contributed to the right to freedom of speech in the United States? Choose the best answer.

A: Selective incorporation required the national government to protect the right to freedom of speech
B: Selective incorporation protected speech that creates a clear and present danger
C: Selective incorporation required that the right to freedom of speech be protected by state governments
D: Selective incorporation required that states restrict speech that is controversial and unpopular

The correct answer is A: Selective incorporation required the national government to protect the right to freedom of speech.