Final answer:
The correct term for a group chosen to represent other customers in marketing research is known as a 'sample'. It's a subset of the entire population intended to reflect the characteristics of the whole group.
Step-by-step explanation:
Companies cannot include every customer in marketing research, so a group, called a sample, is chosen to represent the other customers. The correct answer to the question is a) Sample. A sample is a subset of the larger population chosen for a study to represent the entire group. For instance, if researchers are conducting a survey on college athletes, they would select a sample that accurately reflects the larger population of all college athletes, to ensure the results are generalizable. This method is also used in the Gallup Poll and various scientific research where a random sample increases the reliability and accuracy of the data collected.