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问题 选择题

据统计，自20世纪后期，人类的肆意破坏加剧了物种的灭绝，现在物种灭绝的速度是[ ]

A．100年灭绝一种鸟

B．大约每10年灭绝一种鸟

C．每3年就有两种鸟灭绝

D．大约每50年灭绝一种鸟

答案

答案：C

单项选择题 共用题干题

VRML is a（1）for 3D multimedia and shared virtual worlds on the WWW.In comparison to HTML, VRML adds the next level of interaction,structured graphics,andextra（2）（z and time）to the presentation of documents.The applications of VRMLare（3）,ranging from simple business graphics to entertaining WWW page graphics, manufacturing,scientific,entertainment,and educational applications,and 3D shared virtual worlds and communities. X3D is the name under wluch the development of VRML is continueD.X3D is based on XML andis backwards（4）with VRML.Furthermore,it is componentized,profiled, and extensible,which makes it possible to use X3D in very different（5）,from high-end visualizations to lightweight applications.

空白（5）处应选择（）

A.scenanos

B.places

C.applications

D.programs
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填空题

气瓶上的阀门或减压器气门。若发现有毛病时，应立即（），进行修理。
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