单选题 Scientists have for the first time used cloning to create human embryos that live long enough in a laboratory dish to have their stem cells harvested. The feat could set the stage for physicians to produce cells and tissues, tailored to a patient's genetic identity that can treat a wide variety of human illnesses. The accomplishment also provides a road map for how to clone a person, an even more divisive undertaking.
The new work, performed in South Korea, represents "a major advance in stem cell research. It could help spur a medical revolution as important as antibiotics and vaccines", says Robert Lanza of Advanced Cell Technology (ACT), a company in Worcester, Mass., that's also investigating the promising stem cell strategy called therapeutic cloning.
"However, now that the methodology is publicly available", Lanza adds, "I think it is absolutely imperative that we pass laws worldwide to prevent the technology from being abused for reproductive-cloning purposes."
While some fertility doctors and a religious cult have claimed success at creating a pregnancy via cloning, they've offered no convincing proof. In contrast, the South Korean research is being reported at the meeting of the American Association for the Advancement of Science in Seattle and will appear in an upcoming Science. "This is reality," says stem cell researcher John Gearhart of Johns Hopkins University. "He4'e is a bona fide, refereed journal saying that a human embryo has been cloned and a cell line derived from it."
Although ACT has not yet published a report of a cloned human blastocyst, Lanza says that the South Korean success is "consistent with our own results." Therapeutic cloning appeals to Lanza and physicians because cells made this way could have the same DNA as a patient's cells do and thus avoid rejection after they're transplanted.
Seeking a compromise that would permit this strategy to be pursued, many scientists have called for legislation that would ban cloning to produce a baby but allow the creation of cloned embryos to generate stem cells for research or therapies. "The debate has been very polarized," notes bio-ethicist Laurie Zoloth of Northwestern University in Evanston.

单选题 According to the text, stem cells are hard to obtain because
[A] human embryos are very short-lived outside a human body.
[B] human embryos are extremely hard to be cloned.
[C] human genetic identity is difficult to be defined.
[D] human cloning is strongly opposed by some researchers.

单选题 Successful stem cell research will hopefully lead to
[A] the cloning of any human beings.
[B] the cure of many otherwise incurable diseases.
[C] the abandonment of antibiotics and vaccines.
[D] the realization of human's dream of immortality.

单选题 It can be inferred from the passage that human cloning
[A] has not been so successful as some fertility doctors claim.
[B] will definitely be banned through legislations.
[C] has encountered huge technological and funding problems.
[D] is another project being implemented by South Korean scientists.

单选题 According to the passage, the key factor in avoiding rejection after transplantation is to
[A] make DNAs that are very small and have immune systems.
[B] make DNAs that are as strong as antibiotics and vaccines.
[C] make DNAs that are identical with those in the patients' cells.
[D] make DNAs that are consistent with the ACT research results.

单选题 The "compromise" in the last paragraph probably refers to the practice of
[A] allowing human cloning to be strictly supervised in laboratories.
[B] permitting human cloning to be done in laboratories only.
[C] allowing cloning technology to be used in strictly limited areas.
[D] permitting cloning technology to be used in any field other than medical science.