David walked alone on the road after school.He was upset about the homework he was given today.When he got home,Grandpa was cooking dinner.He dropped his schoolbag on the floor and stepped to his room silently. “Is that you,David?”Grandpa's voice came from the kitchen. “Yes,Grandpa,”David answered.“How was school today?”Grandpa came out and asked. “It was OK,I guess,”David replied,with a small mirthless smile(苦笑) .“You don't look very OK.Why?” Grandpa asked. David told Grandpa about his class project.The teacher asked him to make something with the help of an adult and write a report.But his parents were so busy that they hardly had time to do anything with him. “I don't have anyone to help me,”said David sadly. Grandpa seemed a bit angry.“What am I?”he shouted.“Do you think I am a useless old man?”“Of course not,”David answered immediately.He was surprised and asked,“Are you willing to build a project with me, Grandpa?”“Sure,”Grandpa said. David jumped with excitement.They talked about the project at dinner and finally decided to make a robot. After dinner,they found everything they could use to make it.About an hour later,their work was finished. “What do you think of it?”Grandpa asked. David looked at their strange-shaped robot.“I think its the best robot.”He hugged Grandpa before he went to write his report.“Maybe next time we can make something even cooler,”Grandpa said.