Sports medicine experts have observed for  years that athletes such as long distance runners, especially women athletes, often display a lack of iron. Now a new study by a team of Purdue University researchers suggests that even moderate exercise may lead to reduced iron in the blood of women.   
"We found that women who were normally inactive and then started a program of moderate exercise of middle degree showed sings of iron loss," says Roseanne M. Lyle, associate professor at Purdue. Her study of 62 formerly inactive women who began exercising three times a week for six months was published in the journal Medicine & Science in Sports & Exercise.
Iron deficiency is very common among women in general, affecting one in four female teenagers and one in five women aged 18 to 45, respectively. But the ratio is even greater among active women, affecting up to 80 percent of female endurance athletes. This means, Lyle says, that "too many women ignore the amount of iron they take in". Women of child-bearing age are at greatest risk, since their monthly bleeding is a major source of iron loss. Plus, many health-conscious women increase their risk by rejecting red meat, which contains the most easily absorbed form of iron. And because women often restrict their diet in an effort to control weight, they may not consume enough iron-rich food, and are liable to experience a deficiency.
Exercise can result in iron loss through a variety of mechanisms. Some iron is lost in sweat, and, for unknown reasons, intense endurance exercise is sometimes associated with bleeding of the digestive system. Athletes in high-impact sports such as running may also lose iron through a phenomenon where small blood vessels in the feet leak blood.
There are three stages of iron deficiency. The first and most common is having low iron reserves, a condition that typically has no symptoms. Fatigue and poor performance may begin to appear in the second stage of deficiency, when not enough iron is present to form the molecules(分子) of blood protein that transport oxygen to the working muscles. In the third and final stage, people often feel weak, tired, and out of breath - and exercise performance is severely compromised.
"People think that if they're not at the third stage, nothing is wrong, but that's not true," says John L. Beard, who helped design the Purdue study. "You're not stage 3 until your iron reserves go to zero, and if you wait until that point, you're in trouble."
Beard and other experts say it’s advisable for people to have a yearly blood test. If iron levels are low, talk with a physician to see if the deficiency should be corrected by changing your diet and taking iron-rich foods or by taking iron-added pills.
“Select breads and cereals with the words ‘iron-added’ on the label,” writes sports diet expert Nancy Clark. “This added iron supplements the small amount that naturally occurs in grains.” Clark also recommends cooking in iron pans, as food can obtain iron from the pan during the cooking process.
64．Which of the following may be the title for the passage?
A．Science, sports and exercise
B．Correct iron deficiency
C．Women, Iron and exercise
D．Women, health and exercise
65．The third paragraph is developed mainly by________ .
A．organizing the details according to the order of time
B．presenting the result followed by specific causes
C．beginnign with details followed by a general statement
D．making comparisons ad contrasts
66．What does it mean when you are in the third stage of iron defieiency?
A．Nothing serious though you don’t have much iron stored in the body.
B．There is not enough iron to form the molecules of blood protein to transport oxygen.
C．The small blood vessels in your reet are beginnig to leak blood.
D．No iron is left in your body and you would be in trouble without urgent measures.
67．What is the writer’s attitude in writing this passage?
A．Defensive.       B．Persuasive.      C．Supportive.      D．Objective.