阅]读理解-|||-Every year scientists open more doors that lead to the secrets of new-|||-beneficent drugs.-|||-There is bacitracin,which was discovered by two scientists at Columbia-|||-University's College of Physicians and Surgeons.These two people,Dr.Frank-|||-Meleney and Miss Balbina Johnson,knowing that the human body had some-|||-kind of action in itself with which it fights infections,began to search for the-|||-chemical that does this.In the hospital they examined badly infected wounds-|||-of people who had been hurt in accidents and made tests of the blood and the-|||-infected tissue.-|||-Finally,in the wound of a girl who had broken a leg bone,they found the-|||-useful germs which seemed to be fighting the poisonous infection.They took-|||-some of these into the laboratory and from them developed cultures;that i-|||-larger masses of the germs with which to experiment.At last,after long and-|||-painstaking work,they were able to draw from these germs a substance which-|||-is a germ destroyer.Dr.Meleney and Miss Johnson named it bacitracin -baci-|||-because the germ is,in scientific language,a bacillus and tracin for Margaret-|||-Tracy,whose broken leg supplied the germ.-|||-Bacitracin at first was used only locally; later the drug was developed into a-|||-solution that can be used to fight germs through the blood stream.-|||-1.Today,the discovery of a new drug occurs __-|||-A.very seldom B.once in a generation-|||-C.once every ten years D.frequently-|||-2.Searching for the fighting chemical,the scientists examined __ -.-|||-A.fresh wounds B.infected wounds-|||-C.only infected leg bones D.only a few wounds-|||-3.Cultures,as used in this article,are __-|||-A.masses of germs B.blood tests-|||-C.masses of infected tissue D.poisonous germs-|||-4.Bacitracin __ _.-|||-A.is poisonous B.destroys germs-|||-C.restores broken bones D.develops germs-|||-5.From reading this selection you can infer that __-|||-A.many scientific discoveries are due to chance-|||-B.every year scientists discover new beneficent drugs-|||-C.behind medical discovery there may be a dramatic story-|||-D.cultures are large masses of germs