问题
单项选择题
BCG属于
A．死菌苗
B．减毒活疫苗
C．类毒素
D．抗毒素
E．荚膜多糖疫苗
答案
参考答案：B
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BCG属于
A．死菌苗
B．减毒活疫苗
C．类毒素
D．抗毒素
E．荚膜多糖疫苗
参考答案：B
Which came first, the chicken or the egg? This is one of life’s __1__ questions and people have been debating about it for thousands of years. Now scientists believe they have solved this _2__. Researchers from Sheffield and Warwick Universities in England discovered the answer __3__. They used a super computer to observe the shell-making process while a new shell was __4__. Then they found one protein called OC17 that is __5__ for forming eggshell. This is only found inside a chicken’s body, which is proof that the _6__ came first. The team was __7__ looking at how animals and birds make eggshells but suddenly made their surprising __8__. The big question now is where chickens came from. The _9__ is from dinosaurs. The research team said eggshells are one of nature’s most __10__ creations. Professor John Harding from the team told reporters: “Understanding how chickens make eggshells is fascinating in itself, but it can also be __11__ in designing new materials.” Eggshells are very lightweight but incredibly strong. Even the most up-to-date materials __12__ by the world’s top engineers can not produce anything as __13__ as an eggshell. Professor Harding added that __14__ eggshells could help to cure bone diseases and design materials for the construction industry.“Nature has found wonderful ways that __15__ for all kinds of problems in materials science and technology — we can learn a lot from them.” he said.
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