题目内容：

    Could blood shortages become a thing of the past? Bacterial enzymes (W) from the human gut (肠，内脏)turn type A blood into the type universally accepted for transfusions, and do it more efficiently than current methods.

Our blood comes in four main varieties: A, B, AB and O. The red blood cells in each type are similar in shape, but they have different sugars on their surfaces. Red blood cells in type A host a particular set of these sugars, with type B having a different set. AB blood cells carry both A and B sugars and type O cells have none.

These sugars can act as antigens(抗原),causing an immune response. For instance, transfusing type B blood into someone with type A can cause death. That is what makes anyone with type O blood a universal donor: there are none of these antigens. So being able to remove these sugars from A, B and AB type blood would be helpful, effectively making it usable in transfusions for all.

"We knew that those same sugars that are on our red blood cells are also produced on the inside of the gut wall," says Steve Withers at the University of British Columbia, Canada. So he and his colleagues started searching for bacteria in human waste (粪便)that might make enzymes that let them feed on and break down gut wall sugars.

Analyzing bacterial genes, they found a family of enzymes that help gut bacteria harvest the sugars. When the team combined the enzymes with type A blood, the sugars were removed from the blood cells, resulting in type O blood. The process is 30 times more efficient than an existing one involving other enzymes.

The bacterial enzymes will have to go through more safety testing before they can be used in blood for human transfusions, but it is a promising step, says Withers. He presented the work at a meeting of the American Chemical Society in Boston this week.

1.Why is a man with type O blood a universal donor?

A.The similar shape of his red blood cells.

B.No sugars on his red blood cells.

C.Different sugars on the blood cells.

D.Different quantity of his red blood cells.

2.How do researchers remove the sugars from blood cells?

A.By analyzing bacteria genes.

B.By combining the enzymes with blood.

C.By removing the enzymes from the cells.

D.By involving different enzymes in blood.

3.In which column of the newspaper can this passage be read?

A.Fashion and Lifestyle.

B.Finance and Business.

C.Travel and Sports.

D.Medicine and Health.