题目内容

In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.Spread spectrum simply means that data is sent in small pieces over a number of the (16) frequencies available for use at any time in the specified range. Devices using (17) spread spectrum(DSSS) communicate by (18) each byte of data into several parts and sending them concurrently on different (19) . DSSS uses a lot of the available (20) , about 22 megahertz(MHz). （18）是（）

A. splitting
B. combining
C. packing
D. compacting

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A. splitting B. combining C. packing D. compacting

Questions 11 to 18 are based on the conversation you have just heard.

Questions 11 to 18 are based on the conversation you have just heard.

Questions 11 to 18 are based on the conversation you have just heard.

Passage OneQuestions 26 to 28 are based on the passage you have just heard.

A. splitting
B. combining
C. packing
D. compacting