Question: During the second half of the twentieth century, the Supreme Court's position on free speech was that
A: free speech is essential to liberty and therefore may be abridged only under extreme circumstances
B: the government may never limit speech because free speech is protected by the First Amendment
C: state governments may place limits on free speech, but the national government may not because of the First Amendment
D: the government may limit speech that the majority of Americans finds offensive
Please eliminate two incorrect options first, then think it step by step and choose the most proper one option.