【单选题】
Hair loss is one of those things we still do not understanD、Science has, of
course, shown that men are more likely than women to suffer major hair loss. Some kinds of hair loss are temporary (暂时的), an effect of illness. In those cases we can expect the hair to grow back.It all depends on whether the hair root is alive. If it is not, hair loss is permanent and nothing will help.
Some daily loss of hair is a normal, healthy sign. Most people lose between 40 to 50 scalp hairs each day.Each of these scalp hairs grows for from two to six years and then rests.About three months later it is pushed out by a new hair growing from the same root.This is not something that should cause great concern.Something else we know is that normal hair loss is seasonal, with the most hair loss occurring in the fall.Everyone experiences a normal cycle of loss and growth.The problem of hair loss results when loss is greater than growth.The main cause of hair loss in men seems to be accumulation (积累) of a hormone ( 荷尔蒙) in the body. When that hormone reaches a certain level, the hair growing period is shortened and hair loss is the result. This is no cure for most cases of hair loss. This, however, is not the end of the worlD、