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  3. Blood carries oxygen from the lungs to all the other tissues in the body and, in turn, carries waste products, predominantly car

Blood carries oxygen from the lungs to all the other tissues in the body and, in turn, carries waste products, predominantly car

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问题     Blood carries oxygen from the lungs to all the other tissues in the body and, in turn, carries waste products, predominantly carbon dioxide, back to the lungs where they are released into the air. When【S1】______transport fails, a person dies within a few minutes.  Food that has been processed by the digestive system into smaller components such as proteins, fats, and carbohydrates is also delivered to the tissues by the【S2】______. These nutrients provide the materials and energy【S3】______by individual cells for metabolism(新陈代谢). Waste products produced during metabolism, such as urea(尿)and uric acid, are carried by the blood to the kidneys,【S4】______they are transferred from the blood into urine and eliminated from the body.
    In addition to oxygen and nutrients, blood also transports special【S5】______, called hormones, that regulate certain body functions.  The movement of these chemicals enables one organ to control the function of【S6】______even though the two organs may be located far apart. In this way, the blood【S7】______not just as a means of transportation but also as a communications system.
    The blood is more than a pipeline for nutrients and information; it is also【S8】______for the activities of the immune system, helping fend off infection and fight disease. In addition, blood carries the means for stopping itself from leaking out of the body after an【S9】______The blood does this by carrying special cells and proteins, known as the coagulation(凝结)system, that start to form clots within a matter of【S10】______after injury.

A)chemicals          B)oxygen
C)seconds            D)blood
E)which              F)needed
G)other              H)where
I)responsible        J)another
K)acts               L)available
M)injury             N)hours
O)transports
【S3】
选项
答案F
解析 语法判断，介词by与 needed一起构成后置定语。
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大学英语四级

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