Final answer:
Servers carrying trays of hors d'oeuvres for guests to select from exemplify catered or butler service, which is a type of direct service job found in the tertiary economic sector.
Step-by-step explanation:
The service being described in the student's question is an example of catered service or butler service. This style of service is common in formal settings and events, where servers with platters or trays of hors d'oeuvres walk among guests, allowing them to choose and pick the appetizers they prefer.
The tertiary sector of the economy includes such service jobs, which involve offering a direct service rather than producing goods. Each job within a restaurant, including servers, chefs, janitors, and managers, is specialized to efficiently fulfill the establishment's service goals.