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．for certain

B．for any sake

C．for all

D．for short

无粘性土的抗剪强度指标是（）。