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Every year, 2,000 American lives are saved by the selflessness of others. These are the bone marrow donors who give the gift of life to patients fighting deadly diseases such as leukemia, lymphoma, and aplastic anemia. That’s the good news. The bad news is that thousands more die each year because not enough people have signed on to the registries that would help the ill find a suitable match for a transplant.
Bone marrow or stem-cell transplants are usually a last resort, intended for those whose illnesses have not responded to traditional treatments such as chemotherapy or radiation. How do they work We all store a special type of cell in our bone marrow called stem cells. These primitive cells give rise to the three types of blood cells: red, white and platelets. Everyone’s stem cells have certain genetic characteristics or markers that make them unique from others. Despite this uniqueness, there are some shared characteristics between people. This is impor
A. the same primitive cells can produce the same type of blood cells
B. one’s immune system will reject the blood or organ of different genetic markers
C. one’s immune system will not function well when facing different stem cells
D. the uniqueness of genetic characteristics will destroy the patient’s immune system

[单项选择]Every year, 2,000 American lives are saved by the selflessness of others. These are the bone marrow donors who give the gift of life to patients fighting deadly diseases such as leukemia, lymphoma, and aplastic anemia. That’s the good news. The bad news is that thousands more die each year because not enough people have signed on to the registries that would help the ill find a suitable match for a transplant.
Bone marrow or stem-cell transplants are usually a last resort, intended for those whose illnesses have not responded to traditional treatments such as chemotherapy or radiation. How do they work We all store a special type of cell in our bone marrow called stem cells. These primitive cells give rise to the three types of blood cells: red, white and platelets. Everyone’s stem cells have certain genetic characteristics or markers that make them unique from others. Despite this uniqueness, there are some shared characteristics between people. This is important, because a patie
A. the same primitive cells can produce the same type of blood cells
B. one’s immune system will reject the blood or organ of different genetic markers
C. one’s immune system will not reject the organ of the same type of blood cells
D. the uniqueness of genetic characteristics will destroy the patient’s immune system

[单项选择]Every year more than half a million American kids have drainage(排泄) tubes surgically implanted in their ears to combat persistent infections. The procedure, known as tympanostomy, may not be as (62) as the tonsillectomy was in the 1940s, but it now (63) as the nation’s leading childhood (64) and a new study suggests it’s being vastly overused. In (65) more than 6,000 scheduled ear tube operations, a team of experts (66) by Harvard pediatrician Lawrence Kleinman found that fewer than half were clearly justified. "Each year", the researchers write in the current Journal of the American Medical Association (JAMA), "several hundred thousand children in the United States may be (67) tympanostomy tubes that offer them no demonstrated (68) ...and may place them at increased (69) ."
Tube placement isn’t a (70) risky procedure, but it costs $1,000 to $1,500 and sometimes scars the eardrum, causing a partial loss of (71)