Which situation is an example of a primary election?

A primary election is specifically held to select a party's candidate for the general election. This process is crucial as it allows registered party members to choose their preferred candidate who will represent them in the upcoming general election. In the scenario where Republicans nominate a candidate for president, it clearly denotes the function of a primary election, as it involves a party-specific selection process to determine which individual will carry the party’s banner into the presidential race.

The other choices describe different electoral processes: electing local officials, making decisions through the electoral college, and voting for local government representatives, none of which pertain to the initial steps of party nomination that define a primary election. Thus, option B accurately represents the essence of what a primary election entails, focusing on candidate selection within a political party for higher office.