In Her Research on Mood, Selena Asks Research Participants to Keep

In her research on mood, Selena asks research participants to keep a journal for a period of one month. In this journal, participants write as much as they can about the various emotions they experience each day. Selena's research would best be described as

A) relying on signal-contingent self-reports.
B) high in inter-rater reliability.
C) a narrative study.
D) archival research.