What Is the Significance of the Court's Ruling in Buckley

What is the significance of the Court's ruling in Buckley v. Valeo (1976) ?

A) Consistent with the First Amendment, Congress could limit campaign contributions.
B) Limitation of campaign contributions is a violation of the First Amendment.
C) Congress may limit personal money spent by a candidate on behalf of his own campaign.
D) All campaign finance legislation is unconstitutional.
E) The First Amendment does not apply to campaign spending; Congress has unlimited authority to regulate in this area.