我国北方冬天比较寒冷，许多家庭安装了一种利用电来取暖的床—“韩式电热炕”．其工作电路可简化为如图所示，其中K为保护开关，平常处于闭合状态，当温度超过某一警戒温度时自动断开，扇形导体S为旋转型选档开关，可绕0点旋转，每次都和相邻的两触点同时接触，从而实现关、低、中、高四个档位的转换（档位顺序未知，电功率越大档位越高）．小明在家里利用所学的物理知识来测量该电热炕的电功率．他先关闭家里其它所有的用电器，然后将S旋转到与触点1、2连接，观察发现家里标有“3000r/（kW•h）”的电能表的转盘在1min内刚好转了20转．已知R1和R2是发热电阻，R2的阻值是R1的2倍，其它电阻忽略不计，小明家电压恒为220V．完成下列问题：
看图，给下列图片选择合适的句子或对话。
① ____ A. I have a new dress.
② ____ B. Look at my sweater. It's nice.
③ ____ C. My trousers are too long.
④ ____D. Look at his shirt. It's nice.
⑤ ____ E. In winter, I need a warm coat.
____ A. I have a new dress.
____ B. Look at my sweater. It's nice.
____ C. My trousers are too long.
____D. Look at his shirt. It's nice.
____ E. In winter, I need a warm coat.
名,女教师
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