A. They can in the same way that you do. Your question shows how you are addicted to illusions. Why do you think they can’t practice because they can’t see and hear? If they had no sight, how could they feel that they can’t see? If they had no hearing, how would they realise that they are deaf? The blind and the deaf see and hear in a different way from ours, and have illusions of their own making in their way. If they think they are blind or deaf, the thoughts are also illusions. If they try to realise where such thoughts come from, that is a good Zen practice. They are as likely to reach the final goal, enlightenment, as you are.
Zen Fools 
They may already be more realised than we are.
The best lesson I ever had on caring for others was from an old, disabled lady with the beginnings of dementia. All labels. She was truly herself. She justshowed me.
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