Men cannot manufacture blood as efficiently as women can. This makes surgery riskier for men. Men also need more oxygen because

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问题    Men cannot manufacture blood as efficiently as women can. This makes surgery riskier for men. Men also need more oxygen because they do not breathe as often as women. But men breathe more deeply and this exposes them to another risk. When the air is polluted, they draw more of it into their lungs.
   A more recent and chilling finding is the effect of automobile and truck exhaust fumes on children’s intelligence. These exhaust fumes are the greatest source of lead pollution in cities. Researchers have found thatthe children with the highest concentration of lead in their bodies have the lower scores on intelligence tests and that boys’ score lower than girls. It is possible that these low scores are connected to the deeper breathing that is typical of the male.
   Men’s bones are larger than women’s and they are arranged somewhat differently. The feminine walk that evokes so many whistles is a matter of bone structure. Men have broader shoulders and a narrower pelvis, which enables them to stride out with no waste motion. A woman’s wider pelvis, designed for childbearing, forces her to put more movement into each step she takes with the result that she displays a bit of a jiggle and sway as she walks.
   If you think a man is brave because he climbs a ladder to clean out the roof gutters, don’t forget that it is easier for him than for a woman. The angle at which a woman’s thigh is joined to her knees makes climbing awkward for her, no matter whether it is a ladder or stairs or a mountain that she is tackling.
   A man’s skin is thicker than a woman’s and not nearly as soft. The thickness prevents the sun’s radiation from getting through, which is why men wrinkle less than women do.
   Women also stay cooler in summer. The fat layer helps insulate them against heat. Men’s fat is distributed differently. And they do not have that layer of it underneath their skin. In fact, they have considerably less fat than women and more lean mass. Forty-one percent of a man’s body is muscle compared to thirty-five percent for women, which means men have more muscle power. When it comes to strength, almost 90 percent of a man’s weight is strength compared to about 50 percent of woman’s weight.
   The higher proportion of muscle to fat makes it easier for men to lose weight. Muscle burns up five more calories a pound that fat does just to maintain itself. So when a man goes on a diet. the pounds roll off much faster.
   For all men’s muscularity they do not have the energy reserves women do. They have more start-up energy, but the fat tucked away in women’s nooks and crannies provides a rich energy reserve that men lack.
   Cardiologists at the University of Alabama who tested healthy women in treadmills discovered that over years the female capacity for exercise far exceeds the male capacity. A woman of sixty who is in good health can exercise up to 90 percent of what she could do when she was twenty. A man of sixty has 60 percent left of his capacity as a twenty-year-old.
The main topic of this passage is about ______.

选项 A、the biological differences between men and women
B、the differences in social roles between men and women
C、the differences in living habits between men add women
D、the challenges men and women face from the point of view of biology

答案A

解析 本文主要从blood manufacturing,bones,skin,fat和muscle组成等方面讲述了男性和女性的差异,这些都是生物学方面的差异,选项A正确。
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