Which statement BEST expresses the main idea of this selection?
A) Foot pain can cause pain in other parts of your body.
B) Pro Walk inserts have been proven to help anybody with chronic foot pain.
C) Those who suffer from chronic foot pain should not have jobs that require them to stay on their feet for long periods of time.
D) Evidence suggests that Pro Walk inserts are effective, but those who suffer from chronic foot pain must find an orthotic that fits properly.