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问题 单项选择题

离心式机组抽气装置是取消活塞式压缩机的无泵型，其动作可示为一具（）不断地压缩它上面的空气等不凝性气体。

A.固体活塞

B.液体活塞

C.气体活塞

D.手动活塞式压缩机

答案

参考答案：B

单项选择题

The data station usually means a (71) unit that provides data for transmission, that accepts transmitted data, and that performs all functions necessary for communication with another functional unit. Data stations may be divided into two kinds, the primary stations and the secondary stations, (72) control functions.

In (73) data link control, the primary station is the data station that supports the primary control functions of the data link, generates commands to be transmitted, and interprets received responses. Specific responsibilities assigned to the primary station include initialization of control signal interchange, organization of data flow and actions regarding error control and error recovery functions. The secondary station executes data link control functions as (74) by the primary station, interprets received commands and (75) responses to be transmitted.

（73）处填（）。

A．advanced

B．up-to-date

C．top-level

D．high-level
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填空题

有下列程序：
#include ＜stdio.h＞
main()
char C；
while((c= getchar ())!=’，’) putchar(++c)；

程序运行时，如果从键盘输入：A，B，＜CR＞，则输出结果为______。
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