题目

阅读下列短文，从每题所给的A、B、C和D四个选项中，选出最佳选项。 It may come as a surprise that human beings are not alone in having invented vaccination （疫 苗）. Work just published in the Journal of Experimental Biology by Gyan Harwood of the University of Illinois confirms that honeybees got there first. Being social insects, honeybees are at a constant risk of diseases sweeping through their living places-the beehives. Most animals which live in crowded conditions have particularly strong immune systems, so it long puzzled insect experts that honeybees do not. Part of the answer, discovered in 2015, is that queen bees vaccinate their eggs by passing into them, before they are laid, little bits of proteins from disease-causing virus. These will activate the development of a protective immune response in the developing young. But that observation raises the question of how the queen receives her antigen （抗原）supply in the first place. To find it out, Gyan Harwood teamed up with a group led by Heli Salmela. Together, they collected about 150 nurse bees and divided them among six queenless mini beehives equipped with groups of baby bees to look after. They fed the nurses on sugar-water, and for three of the beehives they mixed the sugar-water with P. larvae, a virus that causes a deadly disease. In this case, tostop such an infection happening, Dr. Harwood and Dr. Salmela heat-treated and so killed the virus in advance. And, sure enough, it's confirmed that some bits of P. larvae were getting into royal jelly （蜂王浆） produced by those bees which had been fed with the mixed sugar-water. Moreover, examination of this royal jelly revealed increased levels, compared with royal jelly from bees that had not been fed with P. larvae, of defensin-1, which is thought to help bee immune systems defend the bees from virus infections. These findings suggest that nurse bees are indeed, via their royal jelly, passing antigens on to the queen for vaccination into her eggs. They also mean, because baby bees, too, receive royal jelly for the first few days after they hatch, that the nurses are vaccinating as well. It seems protective. （1） What has long puzzled insect experts concerning honeybees? A . They live in crowded conditions. B . They do not have strong immune system. C . They are social insects. D . They do not get swept by diseases. （2） When does the queen transfer the antigen to the young bees? A . After they hatch. B . Before the eggs are laid. C . When they are growing up. D . Before her immune system is activated. （3） What is the most important in protecting the young bees from virus infection? A . The sugar-water. B . Royal jelly free from antigens C . Increased defensin-1. D . Care from the professors. （4） Which of the following can be the best title for the text? A . Sweeping Diseases Threaten Honeybees B . Baby Bees Are Vaccinated by the Nurse Bees C . Vaccination Strengthens Honeybees D . Honeybees Run Vaccination Programs, Too 答案： D B C D

查看本题答案和解析