题目

下列关于细胞生命历程的叙述，正确的是 A . 人体细胞的衰老就是人体的衰老 B . 细胞分化导致遗传物质发生改变 C . 脑细胞因缺氧而死亡的现象属于细胞坏死 D . 癌变细胞的呼吸速率降低、核体积增大 答案：C 阅读理解。 　　These days, it's easy to fly across oceans for vacation．Centuries ago, however, crossing the open seas required thorough and accurate planning, handmade boats, and courage．Scientists and historians have long been looking for clues to explain who crossed which oceans first．When it comes to the trip between Polynesia(玻利尼西亚中太平洋群岛)and South America, chickens may have been among the first ocean voyagers, according to new evidence． 　　After studying an ancient chicken bone, anthropologists(人类学家)from the University of Auckland in New Zealand now say that people and chickens traveled from Polynesia to what is now Chile(智利)by about 620 years ago．By then, the Inca people were already living in South America, but the Polynesians would have been the first to get there by sea．Previous theories claimed that European explorers and their chickens sailed to South America first -- but those voyagers didn't arrive until about a century later． 　　In 2002, archaeologists dug up 50 chicken bones from a site in Chile called El Arenal．The team from New Zealand analyzed one to these bones．According to their calculations, the bone is about 650 years old． 　　The researchers also compared the genetic material, or DNA, from the South American chicken bone with DNA from 11 chicken bones that had been found on the Polynesian islands of Tonga and American Samoa．These islands are 6,000 miles west of Chile．The bones found on the Polynesian islands are been 600 and 2,000 years old． 　　Results of the comparisons showed that the chicken bones from both the Polynesian and South American sites had part of DNA in common．The researchers found the same part of DNA in feathers of two living chickens in Chile that belong to a modem breed that lays blue eggs．That DNA evidence suggests a close relationship among the chickens． 　　"However, the weight of scientific evidence is now behind the hypothesis(假设)that it was seafaring(航海)Polynesians who sailed from the islands to South America and returned," says archaeologist Patrick V．Kirch of the University of California, Berkeley． (1) What is the passage mainly about? [　　] A． It was difficult for ancient people to travel between Polynesia and South America． B． The first people who lived in Chile and Polynesia． C． Valuable chicken bones have been found in Chile． D． Chickens－the first to travel between Polynesia and South America． (2) When did the first European explorers reach South America? [　　] A． About 520 years ago． B． About 2.000 years ago． C． About 600 years ago． D． About 620 years ago． (3) People found that chickens were among the first to travel from Polynesia to South America by _________． [　　] A． comparing the colors of eggs laid by chickens from the two places B． comparing the DNA of chicken bones dug up on the Polynesian islands and that of the chicken bones from South America C． studying some previous theories D． asking the natives of South America (4) What do we learn from the passage? [　　] A． European explorers and their chickens were the first to sail to South America． B． Chickens in South America have the same ancestors as those in Polynesia． C． In ancient times, a 6,000-mile channel separated Polynesia from South America． D． Before the Polynesians arrived in South America, the Inca people had lived there．'