A、Physical barriers. B、Ignorance. C、Prejudice. D、Mental illnesses. B题干询问的是对于残疾人来说，最大的障碍是什么。短文中提到，偏见很难破除，无知不可避免地代表着目前最大的障碍，故答案为B)

No one knows exactly how many disabled people there are in the world, but estimates suggest the figure is over 450 million. The number of disabled people in India alone is probably more than double the total population of Canada.
    In the UK, about one in ten people have some disability.(20)Disability is not just something that happens to other people. As we get older, many of us will become less mobile, hard of hearing or have failing eyesight.
    Disablement can take many forms and occur at any time of life. Some people are born with disabilities. Many others become disabled as they get older. There are many progressive disabling diseases. The longer time goes on, the worse they become. Some people are disabled in accidents. Many others may have a period of disability in the form of a mental illness.(21)All are affected by people’s attitude towards them.
    Disabled people face many physical barriers. Next time you go shopping or to work or visit friends, imagine how you would manage if you could not get up steps, or on to buses and trains. How would you cope if you could not see where you were going or could not hear the traffic? But there are other barriers:(22)prejudice can be even harder to break down, and ignorance inevitably represents by far the greatest barrier of all. It is almost impossible for the able-bodied to fully appreciate what the severely disabled go through, so it is important to draw attention to these barriers and show that it is the individual person and their ability, not their disability, which counts.
20. What do we learn about disability?
21. What will affect all the disabled people?
22. What is the greatest barrier for disabled people?