Answer: Option(d) is correct option
Explanation:
Observational study is type of non-experimental research that gives no control to researcher for modifying variable.The researcher has duty of observing and collecting information for analysis.
According to the question,study based on type of exercise that students are indulged in after the school is observational study.As activities will be observed and information will be gathered accordingly.
Other options are incorrect because observation study is not described through difference in time of exercise between girls and boys, feeling of students towards after school track practice and relation between sleep hours and exercise.Thus, the correct option is option(d)