Scientists have several rival theories on the causes of fibromyalgia, a disorder that causes body-wide chronic pain and fatigue. One leading theory holds that conditions such as depression, anxiety, drug use and serotonin deficiency can aggravate or even cause fibromyalgia by interfering with "stage 4," or "deep sleep." This theory is concerned with the function of neuropeptide substance P, which is released in the spinal cord in response to pain and causes nerve endings around the initiating nerves to also become more sensitive to pain. Normally, this mechanism is "reset" during deep sleep. If pain becomes body-wide, however, and the mechanism can not be reset, this process may run out of control. Therefore deep sleep plays a vital role in preventing fibromyalgia.

The theory above on the cause of fibromyalgia rests on which of the following assumptions?

A)The body has a limited amount of control over neuropeptide substance P.

B) Fibromyalgia is a completely preventable disorder, if only other conditions are recognized and treated before it can develop.

C)Deep sleep is necessary to the healthy functioning of the nervous system.

D)The functions of neuropeptides released by the spinal cord must be better understood before a cure for fibromyalgia can be found.

E)Because the causes of fibromyalgia are linked to depression, the disorder should be treated by mental health professionals.