One afternoon in January 1989, Suzan Sharp, 43, and her 8-year-old son, David, were walking hard【C1】______an icy parking lot(停车场),【C2】______Suzan’s cane(手杖)slid on the ice. She【C3】______face-first into the mud. David【C4】______to his mother’s side. 'Are you all right, Mom?'【C5】______, Suzan pulled herself up. 'I'm okay, honey, ' she said. It had been nearly two years since Suzan had trouble walking. She was falling more【C6】______now. Every inch of ice was a【C7】______danger for her. 'I wish I could do【C8】______, ' the boy thought. David, too, was having【C9】______of his own. The boy had a speech defect(缺陷). At school he【C10】______asked questions or read aloud. One day David’s teacher announced a【C11】______assignment. 'Each of you is going to come up with an invention, ' she said. This was for 'INVENT AMERICA !' a national competition to encourage creativity in【C12】______. An idea hit David one evening.【C13】______only his mother’s cane didn’t slip on the ice, he thought. 'That’s it !' David realized. 'What if I fixed your cane to a nail stretched out of the bottom?' he asked his mother. '【C14】______the sharp end would scratch floors, ' Suzan said. 'No, Mom. I could make it like a ball-point pen. You take your hand【C15】______the button and the nail returns back up. ' Hours later the cane was finished. David and his father, Jeff,【C16】______as Suzan used it to walk 50 feet across the【C17】______. 'It works!' she said. In July 1989, David was declared national winner at the annual 'INVENT AMERICA!' ceremony in Washington D. C. As David began to make【C18】______appearances, he was forced to communicate more clearly. To- day, David is nearly【C19】______of his speech defect, and his cane is waiting to be widely used. 【C20】______the boy who once had trouble talking now hopes to start making canes for people who have trouble walking. 【C1】