Final answer:
The unique characteristic of the United States' democracy in selecting political candidates compared to other democracies is the use of primaries. These are party-specific elections that determine who will represent the party in the general election.
Step-by-step explanation:
The question asks about a unique characteristic of the United States' democracy compared to other democracies. Among the options provided, the correct answer is: b. uses primaries to select political candidates. This system of primaries is a process by which political parties in the U.S. select their candidates for elected office to run in the general election. Each party conducts a series of primary elections or caucuses in the various states, and party members vote to choose which candidate will represent them in the general election.
Unlike many other democratic nations, the United States does not have automatic or government responsibility for voter registration, nor does it penalize eligible voters for not voting on election day. Instead, it places the onus on the individual to register to vote. Moreover, the U.S. presidential election features an Electoral College system which indirectly elects the President, making it a unique aspect of the American political process.
Neither elections for the lower house of the legislature every four years, nor an election for the chief executive every six years, nor automatic voter registration, nor penalizing voters for not participating on Election Day are correct options for the United States’ unique democratic process as described in the question.