【概括大意】Deaf people—people who can’t hear—are still able to communicate quite well, with a special language. It’s called sign language. The speaker of sign language uses hand gestures in order to communicate. Basic sign language has been used for a long, long time. But sign language wasn’t really developed until about 250 years ago. In the middle of the 1700’s, a Frenchman named Epee developed sign language. Epee was able to speak and hear, but he worked during most of his life as a teacher of deaf people in France. Epee developed a large number of vocabulary words for sign language. Epee’s system used mostly “picture-image” signs. We call them picture-image signs because the signs create a picture.
The main idea of this paragraph is__________.