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如图所示,是某型号电压力锅简化的工作电路.R0是阻值为484Ω的保温电阻,R1是规格为“220V 800W”的主加热电阻,R2是副加热电阻.用电压力锅分为“加热升压→保压→保温”三阶段,通过如图乙所示的锅内工作压强与时间“(P﹣t)”关系图象可了解其工作过程:接通电源,启动智能控制开关S,S自动接到a.同时S1自动闭合,电压力锅进入加热升压状态;当锅内工作压强达80kPa时,S1自动断开,进入保压状态,当锅内工作压强降至60kPa时,S1又会自动闭合;当保压状态结束,S自动接到b,进入保温状态.

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阅读下面的短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑。

A Welcome Gift

    Dario and his mother loved their new apartment. The living room was large enough for their piano. That night, the two of them 1 side by side at the piano. They played jazz music to celebrate their new home. The loud 2 filled the room and made them feel very happy.

    The next morning, 3, their happiness disappeared. Someone had left a 4 under their door during the night. One of their neighbor had written to complain(抱怨) about the sound of the piano. Dario's mother asked the building superintendent(管理员) if he knew anything about it. But he said that they were all 5 people and he couldn't imagine any of them had done that. Later that morning, Dario suggested that they write a letter to their 6 and apologize for their playing.

    “Maybe we could go and 7 everyone in person.” his mother said. “What if we invited them to come here for a 8 instead? Dario asked. They both loved the 9. Over the next few days, they sent out invitations and prepared desserts 10 their guests. They decorated the apartment with streamers(彩带) and party lights.

    Finally, the day of the party 11. Some guests brought presents. Others brought flowers. Some even brought desserts to 12. One woman, Mrs. Gilbert, 13 Dario's mother with a book of piano music by Chopin.

    “I heard you playing the other night,” she said. “The sounds woke me out of bed. I 14 that you might play like this every night. So I wrote a short note. I hope you don't think I disliked the playing.”

    Dario's mother smiled at Mrs. Gilbert. “I think maybe we 15 you an apology.” she said. “I didn't 16 how late it was when we were playing. Maybe we should play some quieter music at night.

    “You play, you play!” Mrs. Gilbert said. “I like what you play! Just not so loud at night.” She pointed to the book she had given them. “These songs are not such 17 music.”

    “These songs are beautiful music.” Dario's mother said. “We will be 18 to play them in the evening.”

    “And we won't play so loud or late!” Dario said. He was already looking forward to 19 the new music. More than that, however, he was happy to see the big smile on his mother's face. It gave him a feeling of 20 and made him feel that they were home at last.