关于现代生物技术应用的叙述，错误的是[ ] A．蛋白质工程可合成自然界中不存在的

TCP/IP （） are the standards around which the Internet was developed.

A．protocols

B．agreements

C．conventions

D．coordination

供不应求，价格升高，买方占主导地位，属于卖方市场。 [ ]

一瓶气体经化验得知其中只有一种元素，则该气体[ ]

A．肯定是一种单质

B．是一种化合物

C．单质和化合物的混合物

D．可能是一种单质，也可能是几种单质的混合物

短文改错。

    It is interested to visit another country, but sometimes there are some questions when we don't know the

language very well. It may be difficult to talk about the people there. We may not know how to use the

telephone in the country which are visiting. We may not know what to buy the things we need. In a strange

country we may not know where to eat and what to order in a restaurant. It is not easy to decide how many

money to tip (小费) waiters or taxi drivers. When we are helpful, we may not know how to ask help. After

a short time later, however, we learn what to do and what to say. We learn to enjoy life in another country,

and then we may be sorry to leave both the place and the people.

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在带电的电流互感器二次回路上工作时，应采取哪些安全措施？