According to this bbc news article, which branch of the government had to consent to the
treaty of versailles and us participation in the league of nations?

The US Senate, which is part of Congress,  was supposed to ratify the Treaty of Versailles. It voted against it. It is one of its faculties, to ratify any treaty signed by the United States government. It also had to approve joining the League of Nations because becoming a member of an international organization requires signing a treaty of adhesion. In both accounts, president Wilson failed to persuade the Senate to vote in favor of the treaties mentioned above.

Explanation:

with my knoladg i would say it was c