Qingdao edition mathematics first volume exercise book answer.
In the past, there was a horror story circulating in major schools. There was something unclean in a school. Every fifteenth day, the eyes of Lu Xun's portrait at the school gate will move, and all the teaching buildings will be cut off. The stairs will change from the original 13 step to 14 step, and the water discharged from the laboratory faucet will turn red. There is also a toilet at the end of 1 building. A group of people don't believe it. The evil children made an appointment to explore 15. In the evening 12, they arrived at the school gate on time. Lu Xun's eyes looked to the left. They wrote down whether they moved when they were afraid to come out. Why didn't they turn on the switch when they came to the classroom? "Deception." A boy complained, "Look again." Come to the stairs "1 2 3... 13, right?" The children were a little skeptical about the truth of the legend, so they came to the laboratory again and turned on the tap, and shiny water came out. "How boring! We came for nothing! " At first, the excitement was eliminated by half. Finally, they came to the toilet. Although the girl said she didn't believe it, she still didn't dare to go in, so she let Xiao C, who just said she wasn't afraid, go in and look at her watch. Two minutes later, the boy came out. "Everything is a lie." The children broke up in discord. On the way out, a doorman found them and scolded them for staying at school so late. The children ran away. Little B pays special attention to the stone statue at the door. Yes, his eyes are still on the left. He muttered, "hello, little b? Why hasn't Xiao C come back from going out with you last night? " The next morning, little C's mother called to ask. Little C didn't go to school either, and the children vaguely felt that something was wrong, so they told their teachers and parents about their adventures in the evening, and everyone went back to that school accompanied by adults. "What? Our portrait of Lu Xun always looks to the right. " The headmaster said strangely after listening to the children's stories. "But when we came yesterday, we looked left." When we went out, we looked right ... "But there was electricity yesterday." "There was a power outage in our whole area yesterday ... how did you turn on the light?" "There are stairs!" The children ran quickly to the stairs "1 2 3... 12? ""Our stairs have always been 12. " "Impossible! ! ! ""and the lab, "a child warned. "Yes, the laboratory" a line of people came to the laboratory. There was a dark red mark under the tap they turned on yesterday. "It's blood." "So ... little C went to the toilet yesterday ..." Everyone felt scared. "Let's go and have a look." The headmaster also realized the seriousness of the matter ... pushed open the door ... and the body of Xiao C suddenly appeared in front of everyone because of panic. His eyes were wide open, his throat was cut, and his bloody internal organs were scattered in the pool that had been killed ... "Ah ..." Xiao C's mother fainted on the spot, and several teachers rushed out at once. Vomiting ... little b was shocked. One second before he passed out, he caught a glimpse that the pointer of Xiao C's watch stopped at 1 ... At this time, Xiao C went in ... By the way, there was no doorman on the night of their expedition ... If you transfer this post to more than five forums, you won't be haunted by demons, and you can realize a wish. People who don't reply often ... sorry, I'm helpless, too.