B
題意:
根據(jù)第4段,異種器官移植的主要問題是什么?
A.病人的想法。B.身體的排斥。C.價格高。D.器官的數(shù)量。
根據(jù)第四段Doctors have experimented(試驗)with xenotransplantation since the early20th century. There are few success stories. Usually, patients' bodies reject(排斥) the animal organs. Bennett lived much longer than other xenotransplantation patients. That's because scientists removed(去掉) pig genes(基因) that would cause fast rejection. Then they added human genes to help the body accept the organ. 自20世紀初以來,醫(yī)生們就開始試驗異種器官移植。很少有成功的故事。通常,病人的身體會排斥動物器官。貝內(nèi)特比其他異種移植患者活得更長。這是因為科學家們移除了會導致快速排異反應的豬基因。然后他們添加了人類基因來幫助身體接受器官??芍?,異種器官移植的主要問題是身體的排斥,故選B。