Dr$.$ Rubin's research project focuses on people's opinions toward abortions. She is interested in getting extensive and detailed information from each person in her study. Although this may be expensive and time consuming, she has received a large grant to hire several students to help her. Which research method is Dr$.$ Rubin most likely using?

a$)$ survey

b$)$ focus group

c$)$ in$-$depth interview

d$)$ secondary analysis