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"What's this?" Bob asked, pointing at a wooden box on the sidewalk (人行道). The sign on it said Little Free Library.
"I've heard of those," Bob's elder sister Lily said. "People make them and put books 1. Other people take away the books they want and add the 2 they've already read."
"I want to make something like that," said Bob, "for kids to exchange books."
"What if (要是……会怎么样) it doesn't work?" Lily asked.
"Why wouldn't it 3?" asked Bob. Lily shrugged(耸肩), "Maybe kids won't notice it, or maybe they won't want to 4 their books."
"I'd like to try anyway," Bob said. "Will you help me make one?" "Sure," Lily said. "I'll also ask Dad for 5."
Bob ran inside to collect books while Lily talked to Dad. With Dad's help, they 6 a wooden box. They put a door on it and attached(固定) the box to a post(桩). Then they dug a hole in their front yard and lifted the post into the hole.
Bob put the books inside the box and closed the 7. "Now I just have to wait," he said. Three times that day, Bob ran outside to check. 8 each time his books were the only ones inside.
For the next few days, Bob 9 the box again and again. However, his books were still there. "I guess you were right, Lily," Bob said. "No kids want to exchange books." "I know you really wanted your 10 work, Bob," Lily said. "I'm sorry it didn't."
The next two days, Bob didn't check the box. "Aren't you going to check your little 11, Bob?" Lily asked. "Maybe 12 decided to exchange. You can go and have a look."
Bob walked slowly to the box. He opened the door. His books were gone. Instead, the box was 13 with new books. "Wow, it worked!" Bob shouted excitedly.
Indeed, it was Lily who helped her brother Bob. She called all the 14 kids in the neighborhood and asked them to tell their younger sisters and brothers.
Bob's idea worked 15. He was very lucky to have new books to read and a very good sister.