题目内容：

Virtual (虚拟的) reality is a way to create a computer-made environment that brings the user into a virtual world. If you ever have put on a VR headset, you would know exactly what I am talking about. From an experiential view we do understand the idea, but what about the technical backend that goes into making it all possible? In this blog, we will understand the technology behind virtual reality and the basic terms about the development of a virtual ecosystem for a VR headset.

The primary subject of virtual reality is simulating (模拟) the vision. Every headset is to perfect their method to create an immersive (浸入式) 3D environment. Each VR headset puts up a screen or two in front of eyes, keeping the user away from any interaction with the real world. Two autofocus lenses (自动对焦镜片) are generally placed between the screen and the eyes that change based on eye movement and positioning. The vision appears on the screen either by using a mobile phone or HDMI line connected to a PC.

To create a truly immersive virtual reality, there are certain requirements — a frame rate (帧率) of at least 60 fps, a refresh rate and at least 100-degree field of view ( though 180 degrees is perfect). If either of these doesn’t work according to the standards, the user will experience too big of a time difference between their actions and the response from the screen. We need the response to be less than 20 ms ( 1/1000 second) to fool the brain which is achieved by joining all the above in the right proportion (比例). Another matter that needs to be looked at here is to prevent netsickness because of the differences between the frame rate and refresh rate.

Apart from the image, there are certain other things that go into creating an immersive VR experience, holding the user’s attention completely in the virtual environment. For example, sound effects, when put with the image, can create very attractive effects. By using a headphone and 3D sound effects, the user can totally believe in the virtual environment. While perfecting sound effects, proper care needs to be taken about the consistency (一致) between the pictures and the sound. If you start playing frightening music in the background of a happy scene, it will just put the user off.

In future, we will see rapid progress in creating a truly immersive digital experience. With leading players like Google, Microsoft, Oculus, and HTC making great efforts to improve the capabilities (性能), we are not far from achieving a virtual reality that would feel so much better than the real world. If you would like to develop a VR app for your business, then feel free to get in touch. With over 10 years of experience in mobile technologies, we can make every dream a reality.

1.A VR headset helps the user _________.

A. create the vision on the screen

B. understand the technical backend

C. better experience a 3D environment

D. keep interaction with the real world

2.The words "put the user off" in Paragraph 4 probably mean "__________".

A. take the user’s attention away

B. get the user interested

C. hold the user’s imagination back

D. help the user understand

3.What is the main purpose of writing this passage?

A. To give a short introduction of VR.

B. To do business with certain readers.

C. To predict the bright future of VR.

D. To share experiences with readers.

4.What can we learn from the passage?

A. The lower degree field of view, the better images.

B. Sound effects are more important than the image for VR.

C. Some big companies may create a VR better than the real world soon.

D. The brain can tell the time difference when the response is more than 20 ms.