单选题 Dr Thomas Starzl, like all the pioneers of organ transplantation, had to learn to live with failure. When he performed the world's first liver transplant 25 years ago, the patient, a three-year-old boy, died on the operating table. The next four patients didn't live long enough to get out of the hospital. But more determined than discouraged, Starzl and his colleagues went back to their lab at the University of Colorado Medical School. They devised techniques to reduce the heavy bleeding during surgery, and they worked on better ways to prevent the recipient's immune system from rejecting the organ — an ever-present risk.
But the triumphs of the transplant surgeons have created yet another tragic problem: a severe shortage of donor organs. "As the results get better, more people go on the waiting lists and there's wider disparity between supply and need," says one doctor. The American Council on Transplantation estimated that on any given day 15000 Americans are waiting for organs. There is no shortage of actual organs; each year about 5000 healthy people die unexpectedly in the United States, usually in accidents. The problem is that fewer than 20 percent become donors.
This trend persists despite laws designed to encourage organ recycling. Under the federal Uniform Anatomical Gift Act, a person can authorize the use of his organs after death by signing a statement. Legally, the next of kin can veto these posthumous gifts, but surveys indicate that 70 to 80 percent of the public would not interfere with a family member's decision. The biggest roadblock,according to some experts,is that physicians don't ask for donations, either because they fear offending grieving survivors or because they still regard some transplant procedures as experimental.
When there aren't enough organs to go around, distributing the available ones becomes a matter of deciding who will live and who will die. Once donors and potential recipients have been matched for body size and blood type,the sickest patients customarily go to the top of the local waiting list. Beyond the seriousness of the patients' condition,doctors base their choice on such criteria as the length of time the patient has been waiting, how long it will take to obtain an organ and whether the transplant team can gear up in time.

单选题 Which of the following is true according to the text?

单选题 One factor causing death on organ transplantation is______.

单选题 In the US,there is a long waiting list for organs because ______.

单选题 There would be many more organ donors if______.

单选题 The best title for this passage might be "______".