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In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.Microwave communication uses high-frequency (26) waves that travel in straightlines through the air. Because the waves cannot (27) with the curvature of the earth, they can be (28) only over short distance. Thus, microwave is a good (29) for sendingdata between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or (30) . These can be installed on towers, high buildings, and mountain tops. (27)是()

A. reflex
B. distort
C. bend
D. absorb

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In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.Microwave communication uses high-frequency (26) waves that travel in straightlines through the air. Because the waves cannot (27) with the curvature of the earth, they can be (28) only over short distance. Thus, microwave is a good (29) for sendingdata between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or (30) . These can be installed on towers, high buildings, and mountain tops. (30)是()

A. repeaters
B. radars
C. telephones
D. antennas

The purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable (6) of the technical requirements for the software product. During the requirements definition phase, the requirements definition team uses an iterative process to expand a broad statement of the system requirements into a complete and detailed specification of each function that the software must perform and each (7) that it must meet. The starting point is usually a set of high level requirements from the (8) that describe the project or problem.In either case, the requirements definition team formulates an overall concept for the system and then defines (9) showing how the system will be operated publishes the system and operations concept document and conducts a system concept review(SCR).Following the SCR, the team derives (10) require merits for the system from the high level requirements and the system and operations conceptusing structured or object-oriented analysis, the team specifies the software functions and algorithms needed to satisfy each detailed requirement. (6)是()

A. function
B. definition
C. specification
D. statement

In low-speed network, it is usually adequate to wait for congestion to occur and then react to it by telling the source of packets to slow down. In high-speed networks, this approach often works poorly, because in the (61) between sending the notification and notification arriving at the source, thousands of additional (62) may arrive. In ATM network, a major tool for preventing (63) is (64) control. When a host wants a new virtual (65) , it must describe the traffic to be offered and the service expected. (61)是()

A. interval
B. time
C. slot
D. delay

Packet-switching wireless networks are preferable (41) when transmissions are (42) because of the way charges are (43) per packet. Circuit-switched networks are preferable for transferring large files or for other lengthy transmissions because customers are (44) for the (45) of time they use the net-work. (42)是()

A. long
B. short
C. large
D. small

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