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问题 选择题

In order to protect the environment。supermarkets and stores are forbidden to      free

plastic bags to shoppers．

A．put away

B．put off

C．give off

D．give away

答案

答案：D

多选题

下列除去杂质的方法中，正确的是（　　）

A．用氢氧化钠溶液除去二氧化碳气体中混有的氯化氢

B．用氯化钙溶液除去混在氯化钠溶液中的碳酸钠

C．用稀盐酸除去热水瓶胆的壁上沉积的水垢

D．用稀硫酸除去氢气还原氧化铜实验后试管壁上附着的红色物质
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单项选择题

For each blank, choose the best answer from the four choices and write down on the answer sheet.
(66) is a one-way function that takes an arbitrarily long piece of plaintext and from it computes a fixed-length bit string.
(67) is a protocol that most USENET machines now use it to allow news articles to propagate from one machine to another over a reliable connection.
(68) is an approach preferred by cable TV providers. In this solution the fiber terminates at an optoelectrical converter and the final segment is a shared coaxial cable.
(69) is a device used to connect two separate network that use different communication protocol.
(70) is a digital-to-digital polar encoding method in which the signal level is always either positive or negative.

A．MD

B．RSA

C．DES

D．MIB
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