根据材料请回答 31～35 题
Dr Thomas Starzl, like all the pioneers of organ transplant, had 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 did not 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(发明)techniques to reduce the heavy bleeding during surgery, and they worked on better ways to prevent the recipient' s immune system(免疫系统) from rejecting the organ- an ever-present risk.Now, thanks to further refinements, about two thirds of all liver-transplant patients are living more than a year.
But the triumphs of the transplant surgeons have created another tragic problem: a severe shortage of donor organs."More and more people go on the waiting lists and there is wide disparity(差异)between supply and need," says one doctor.The American Council on Transplantation estimates that on any given day 15,000 Americans are waiting for or-gans.There is no shortage of actual organs; each year about 25,000 healthy people die un-expectedly in the United States, usually in accidents.The problem is that fewer than 20% become donors.
This trend persists despite laws designed to encourage organ recycling.Under the federal 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(否决)these posthumous(死后的)gifts, but surveys indicate that 70% to 80% of the public would not interfere with a family member's decision.The bigger roadblock, according to some experts, is that physicians do not ask for donations, either because they fear offending grieving survivors or because they still regard some transplant procedures as experimental.
When there are not enough organs to go around, distributing the available ones be-comes a matter of deciding who will live and who will die.Once donors and potential recip-ients have been matched for body size and blood type, the sickest patients customarily go to the top of the local waiting list.Besides the seriousness of the patient's condition, doc-tors base their choice on such criteria as the length of time the patient has been waiting and how long it will take to obtain an organ.
第 31 题 Which of the following statements is true according to the passage？

All the patients whom Dr.Starzl operated on died on the operating table.
B. To Dr.Starzl, it was very discouraging that his first liver transplant operation failed.
C. Many doctors had performed liver transplant before Starzl,
Dr.Starzl did not give up though he had failed in his attempts.