[单项选择]

Pain is easier to endure if you know you can end it. Speakers at a session on pain at the British Association’s psychology section have new evidence to support this idea for two common experiences of pain: in childbirth and at the dentist’s. On the other side of the coin, their inability to control pain may explain why some people with continual pain have psychological problems as well.
Dr. J. Robinson found out about the phenomenon of self-controlled pain almost by accident. He was studying the effects of analgesics used to control pain during childbirth and as part of the experiment made it possible for women having their child to press a button which gave an automatic injection—instead of having all injections made by the doctor. Afterwards these women did not say that they had less pain than other women in childbirth, but they did use considerable less of the drug.
J. Atkins, a dental surgeon, has observed a similar phenomenon. As part of the
A. In other words.
B. On the other hand.
C. On the other side.
D. As the only complement to this.