单项选择题：在结点加密方式中，如果传输链路上存在n个结点，包括信息发出源结点和终止结点，则传输路

题型：单项选择题

Air is a colorless, tasteless and invisible（看不见的）gas that is around us. An “empty” drinking glass and an “empty” room, in fact, are not really empty. Each is filled with air. When the glass is filled with water, the water pushes the air out of the glass.

Air, as a gas, has no definite shape, but because it is matter, it takes up space and it has weight. It is easy to prove that air is something that takes up space. Stuff a piece of dry cloth（布）into the bottom of a glass so that it will not fall out when the glass is turned upside down. Push the upside down glass, holding straight up and down, into a jar of water till the glass is completely covered. When the glass is taken out of the water, the cloth is still dry. The air inside the glass shows that it takes up space and keeps the water from coming in.

小题1:Since air is matter, it has ________.

A．room , and weight as well

B．both room and shape

C．either room or weight

D．neither shape nor weight小题2:The word “Stuff” means ______ in Chinese.

A．撕

B．盖

C．取掉

D．塞小题3:The writer tells that the experiment（实验）___________.

A．is carried out in the space

B．must be done in the lab

C．is made in the room

D．can only be done in the open air

查看答案

在结点加密方式中，如果传输链路上存在n个结点，包括信息发出源结点和终止结点，则传输路

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