A．Doubtful.
B．Supportive.
C．Indifferent.
D．Objective.

A．It can reduce the risk of heart disease.
B．It can improve the effect of exercise.
C．It can make us feel happy.
D．It can cure some mental diseases.

A．By collecting information from the Internet.
B．By assessing ten different studies involving many participants.
C．By doing outdoor activities such as climbing and swimming.
D．By organizing many participants listening to different types of music.