题目内容
The main idea of the passage would be__________.
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A．possessB．holdC．possessionD．possessing
The students had a lot of trouble concentrating on their study because of the noise from the construction Outside.
根据材料请回答 31～35 题
Types of Blood
You have been badly injured in a car accident.It is necessary to give you a blood transfusion because you lost a great deal of blood in the accident.However, special care must be taken in selecting new blood for you.If the blood is too different from your own, the transfusion could kill you.There are four basic types of blood： A, B, AB, and O.A simple test can indicate a person's blood type.
Almost everybody is born with one of these four.types of blood.Blood type, like hair color and height, is inherited from parents.Because of substances(物质)contained in each type, the four groups must be transfused carefully.Generally, A and B cannot be mixed.A and B cannot receive AB, but AB may receive A or B．O can give to any other group; hence, it is often called the universal donor(万能献血者). For the opposite reason, AB is sometimes called the universal recipient(接受者). However, because so many reactions can occur in transfusions, patients usually receive only salt or plasma (血浆) until their blood can be matched as exactly as possible in the blood bank of a hospital.In this way, it is possible to avoid any bad reactions to the transfusion.
There is a relationship between your blood type and your nationality.Among Europe-ans and people of European ancestry(祖先), about 42 percent have type A while 45 per-cent have type O.The rarest is type AB．Other races have different percentages.For ex-ample, some American Indian groups have nearly 100 percent type O.
第 31 题 If a patient can receive type A blood, __________.
Nerve signals may travel through nerve or,muscle fibers at speeds as high as two
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