题目内容：

    Scientists may have found a way to reduce shortage of type O blood. Type O is the kind of blood that hospitals most often need. What the researchers are testing is an easier way to make type O blood out of other kinds of blood.

There are four main kinds of blood. Most people born with one of these four: Type A,Type B, Type AB or Type O. Type O can be safely given to anyone. So it is commonly used when a person is injured or sick and has to have blood.

The differences among blood types are linked to whether or not red blood cells contain certain kinds of sugar molecules(分子). These molecules are found on the surface of the cells.They are known as antigens (抗原). These antigens are found with type A, B and AB blood but not with type O.

More than twenty-five years ago, scientists found that the antigens could be removed to create what they called universal-type cells. They could be removed with chemicals called enzymes(酶). But large amounts of enzymes were required to make the change.

Doctor Henrik Clausen of the University of Copenhagen in Denmark led the study. The next step, he says, is to complete safety tests. The team is working with the American company ZymeQuest to test the new method. If it meets safety requirements(*k)and is not too costly,it could become a widely used life-saving tool to increase the supply of universal blood.

1.How do scientists deal with the problem of lacking type O blood?

A.Hope more people to donate type O blood.

B.Make the most of the present type O blood.

C.Develop new ways of using type O blood.

D.Make type O blood out of other kinds of blood.

2.What make people have different kinds of blood?

A.Sugar molecules in red blood cells.

B.People's different living conditions.

C.Peoples various immune systems.

D.The variety of peoples cells and genes.

3.What can we infer from the text?

A.Type O blood can be safely given to anyone

B.Antigens could easily be removed to create universal blood.

C.A Danish company wanted to involve itself in studying blood.

D.The new method is not safe enough to be put into use in hospitals now.

4.What is the best title for the text?

A.Four different kinds of blood

B.A new way to make type O blood

C.The latest research on blood type

D.Find the proper type of blood