A、Sign languages. B、Natural languages. C、Artificial languages. D、Genuine languages. A

My friend, Vernon Davies, kept birds. One day he phoned and told me he was going away for a week. He asked me to feed the birds for him and said that he would leave the key to his front door in my mailbox.
  Unfortunately, I forgot all about the birds until the night before Vernon was going to return. What was worse, it was already dark when I arrived at his house. I soon found the key Vernon gave me could not unlock either the front or the back door. I was getting desperate. I kept thinking of what Vernon would say when he came back.
  I was just going to give up when I noticed that one bedroom window was slightly open. I found a barrel and pushed it under the window. As the barrel was very heavy, I made a lot of noise. But in the end, I managed to climb up and open the window.
  I actually had one leg inside the bedroom when I suddenly realized that someone was shining a torch up at me. I looked down and saw a policeman and an old lady, one of Vernon’s neighbors. "What are you doing up there?" said the policeman. Feeling like a complete fool, I replied, "I was just going to feed Mr. Davies’s birds."

Sign language has become a scientific hot button. Only in the past 20 years have specialists in language study realized that sign languages are unique--a speech of the hands. They offer a new way to probe how the brain generates and understands language, and throw new light on an old scientific controversy: Whether language, complete with grammar, is something that we are born with, or whether it is a learned behavior. The current interest in sign language has roots in the pioneering work of one rebel teacher at Gallaudet University in Washington, D.C., the world’s only liberal arts university for deaf people.
  When Bill Stoke went to Gallaudet to teach English, the school enrolled him in a course in signing. He had been taught a sort of gesture code, each movement of the hands representing a word in English, At the time, American Sign Language (ASL) was thought to be no more than a form of pidgin English. But Stoke believed the "hand talk" his students used looked richer. He wondered: Might deaf people actually have a genuine language? And could that language be unlike any other on earth? Stoke devoted his time to writing and editing books and journals and to producing video materials on ASL and the deaf culture. For decades educators fought his idea that sign languages are natural languages like English, French and Japanese.