If a Health Psychologist Wants to Know If Regular Exercise

If a health psychologist wants to know if regular exercise improves people's health,the type of hypothesis the psychologist would use is

A) one-tailed because the study is only interested in whether the exercise increases health.
B) one-tailed because the study only looks at the effects of exercise and does not consider other factors.
C) two-tailed because the study will have to involve both healthy and unhealthy people.
D) two-tailed because no direction for any observed difference has been predicted.