药材血竭的性状鉴别特征是（） A.呈不规则块状或脂膏状，块状者质地似蜡，脂膏状者黏稠

把（2千米）：（150米）化成最简单的整数比是______：______，它们的值是______．

在地下工程施工中，影响施工技术选择的主观因素是( )。

A．洞室围岩的性质

B．洞室的断面形式

C．洞室的断面尺寸

D．施工技术装备

E．施工技术水平

（）材质的气缸形式较多，形状复杂。

A.铸铁

B.铸钢

C.锻钢

D.碳钢

Virtual reality (or VR (1) ) is kind of a buzzword these days in computer graphics.VR is artificial reality created by a computer that is so enveloping that it is perceived by the mind as being truly real.VR exists in many (2) .A traditional view of virtual reality uses headsets and data gloves.The headset serves as the eyes and ears to your virtual world,projecting sights and sounds generated by the computer.The data glove becomes your hand,enabling you to interact with this (3) world.As you move your head around,the computer will track your motion and display the right image.VR is the most demanding (4) for computer graphics,requiring hardware and software capable of supporting realtime 3D (5) .

A．image

B．Figure

C．Logo

D．graphics

影响城市地域功能分区的主要经济因素是（）

A.社会知名度

B.人们收入的多少

C.付租能力的高低

D.历史背景