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问题 单项选择题

P0是以a为边长的正方形，P1是以P0的四边中点为顶点的正方形，Pn是以Pn-1的四边中点为顶点的正方形（n=1，2，3，…），则当n无限增大时，P1+P2+P3+…+Pn+…的面积为（）。

A.a2

B.2a2

C.3a2

D.4a2

答案

参考答案：A

解析：

显然有，则P0=a2，，故

判断题

圆盘式静电喷枪分为电动和气动两种。( )
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单项选择题

MIDI enables people to use (11) computers and electronic musical instruments. There are actually three components to MIDI, the communications" (12) .", the Hardware Interface and a distribution (13) called "Standard MIDI Files". In the context of the WWW, the most interesting component is the (14) Format. In principle, MIDI files contain sequences of MIDI Protocol messages. However, when MIDI Protocol (15) are stored in MIDI files, the events are also time-stamped for playback in the proper sequence. Music delivered by MIDI files is the most common use of MIDI today.

（11）是（）

A.personal

B.electronic

C.multimedia

D.network
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