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问题 单项选择题

患儿，3岁。吃瓜子时误吸入气管引起窒息。其病因是（）

A.乳食因素

B.先天因素

C.情志因素

D.意外因素

E.其他因素

答案

参考答案：D

解析：常见病因有外感六淫、疠气，饮食内伤，胎产损伤，禀赋不足，意外。先天因素是儿科特有的病因。

单项选择题

VRML is a (71) for 3D multimedia and shared virtual worlds on the WWW. In comparison to HTML, VRML adds the next level of interaction, structured graphics, and extra (72) (z and time) to the presentation of documents. The applications of VRML are (73) , 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 which the development of VRML is continued. X3D is based on XML and is backwards (74) with VRML. Furthermore, it is componentized, profiled, and extensible, which makes it possible to use X3D in very different (75) , from high-end visualizations to lightweight applications.

A．inconsistent

B．independent

C．applicable

D．compatible
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单项选择题

光纤中，能量主要集中在（）。

A.包层

B.芯层

C.涂覆层

D.内层
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