You can become a member of a political party by registering to vote with the party you wish to join. Option B is correct.
The current political party system in the U.S. is a two-party system dominated by the Democratic Party and the Republican Party. These two parties have claimed victory in every United States presidential election since 1852 and have controlled the United States Congress to some extent since at least 1856.
By registering to vote to one of those political parties, you to have a voice in primary elections. Besides, it allows you to vote in general elections.
