Dr Klein Implemented a Study Examining Sleep Patterns and Mood

Dr. Klein implemented a study examining sleep patterns and mood in various environments. Participants in his study were asked to sleep in six distinct conditions: room temperature between 50 and 60 degrees Fahrenheit; room temperature between 61 and 70 degrees Fahrenheit; room temperature between 71 and 80 degrees Fahrenheit; room temperature between 81 and 90 degrees Fahrenheit; room temperature between 91 and 100 degrees Fahrenheit, and room temperature between 101 and 110 degrees Fahrenheit. Dr. Klein immediately began collecting data during the first experimental condition and continued to assess participants' sleep patterns and subsequent mood for each temperature condition. Dr. Klein is conducting a:

A) Latin square design.
B) longitudinal design.
C) repeated-measures design.
D) pretest-posttest design.