Suppose that there is a mute person who wants to buy a toothbrush. By imitating the action of brushing one's teeth, he successfully expresses himself to the shopkeeper and the purchase is done.
Now suppose that there is a blind man that wishes to buy a pair of sunglasses. How should he express himself?
He opens his mouth and says, "I would like to buy a pair of sunglasses." If you got this wrong......you should not tell anyone.