A．there is a mistake in it

B．there is a delay between the movement of the eyes and the wheelchair

C．it costs much and few people can afford it

D．it can't follow the user's wish exactly

26．The new wheelchair being developed will ．

A．use a screen­based system to let the user move

B．avoid the risks of being blocked in the way

C．move directly in the direction the user wants to go

D．determine the user's moving direction

27．What can we infer from the text?

A．The price of the new wheelchair will not be very high.

B．The new wheelchair can move very fast.

C．People can buy the new wheelchair in the market now.

D．The new wheelchair is mostly conducted by hardware.

28．The author of the text aims to ．

A．stress the importance of a new wheelchair

B．make the new wheelchair widely used

C．explain the process of developing a wheelchair

D．introduce a system developed by scientists

　　　　　　　　　　　　　C

The voice in your head is a lie. What you hear when you open your mouth is distinctly less beautiful than what everyone around you hears.

Your voice emanates from the lower portion of your throat，as expelled air from the lungs passes across your vocal chords (声韧带)，which vibrate (振动) to produce sound. This sound is then made louder by your voice box，changed into words by your tongue and lips，and spread through the surrounding atmosphere until it enters your listener's ear canal to stimulate their eardrums (鼓膜) and structures within the inner ear-which then convert the analog waveform (模拟波形) to electrical impulses that the brain can understand.

However，the inner ear doesn't just pick up sound from external sources. Vibrations coming from within your body can activate these auditory (听觉的) structures as well. And when you speak，the rapid fluttering of your vocal chords actually causes your entire braincase to vibrate."When you speak，the vocal folds in your throat vibrate，which causes your skin，skull and oral cavities to also vibrate，and we perceive this as sound，"Ben Hornsby，a professor of audiology at Vanderbilt University，said.

But sound doesn't travel through bone nearly as easily as it does through air. This effect is heightened by the fact that you really can't hear your own voice directly，because your ears are positioned behind your mouth，and the sounds coming out of your mouth must first bounce off objects and back into your ears. This，too，causes the waveform to lose energy as well as frequency and pitch，resulting in you hearing a distorted，lower tone than what people hear directly from out of your mouth.

"You hear your voice in stereo，" Michael Kelly said，"while other people just hear it in mono (单声道)．" That's why you may think you sound like James Earl Jones in your head，but end up sounding like Steve Urkel on tape.

29．What is the main idea of the text?