单选题：根据以下材料，回答题Sign has become a scientific hot button. Only in t

根据以下材料，回答题
Sign has become a scientific hot button. Only in the past 20 years have specialists in language　study realized that signed languages are unique--a speech of the hand. 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 Stokoe went to Gallaudet to teach English, the school enrolled him in a course in　signing. But Stokoe noticed something odd: Among themselves, students signed differently from his　classroom teacher.
Stokoe had been taught a sort of gestural 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 (混杂英语). But Stokoe 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? It was 1955, when even deaf people dismissed their signing as"substandard!'. Stokoe' s idea was academic heresy ( 异端邪说).
It is 37 years later. Stokoe--now devoting his time to writing and editing books and journals　and to producing video materials on ASL and the deaf culture--is having lunch at a cafe near the　Gallaudet campus and explaining how he started a revolution. For decades educators fought his　idea that signed languages are natural languages like English, French and Japanese. They assumed　language must be based on speech, the modulation(调节) of sound. But sign language is based on　the movement of hands, the modulation of space. "What I said," Stokoe explains, "is that language is
not mouth stuff--it's brain stuff."
The study of sign language is thought to be （　　）. A．a new way to look at the learning of language
B．a challenge to traditional, views on the nature of language
C．an approach to simplifying the grammatical structure of a language
D．an attempt to clarify misunderstanding about the origin of language