Ruth is conducting a case study of typical ways of working in a college registrar's office. Of the following, which is appropriate practice for Ruth as she selects participants for her study?

a. Ruth should select all workers as participants for her identified case.

b. Ruth should screen potential participants and include only those who can contribute to her understanding.

c. Ruth should screen potential participants and include those with a strong perspective.

d. Ruth should allow the administrator in the office to select the participants given their individual roles in the context.