Ronald is a sociologist carrying out a study on the labor unions of companies in the manufacturing sector. He selects a set of companies for his study. When observing the workers of an automobile company, he notices that the line supervisors dominated the conversations among the workers. Ronald realizes that his study would not be complete without the help of these line supervisors. Hence, the line supervisors are called Blank______. Multiple choice question. focus group members key informants sample representatives complete observers