Dr. mitchell is conducting a research study on temperament. as a basis of this study, he plans to follow 1,000 subjects from the age of 5 to the age of 35. at periodic times he will revisit subjects and their temperament. dr. mitchell’s research study is planned to last for 30 years. which of the following best describes the type of research dr. mitchell is conducting? 1. ethnographic research2. quasi-experimental research3. longitudinal research4. cross-sectional research