—Is it summer? —No, it's____．It's____and dry．

把“同位角相等”写成“如果…那么…”的形式为：为____．

给下列图片排序。    There are some special days in a year.New Year's Day is in January.Then Tree Planting Day comes after Women's Day.Children like June best.Because Children's Day is in June.Dragon Boat Festival (端午节) always comes after Children's Day.I like Children's Day，because I can play many games and get some gifts from my parents on that day.In September we have Teachers' Day.And in October，we have China's National Day.
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某校用420元钱到商场去购买“84”消毒液，经过还价，每瓶便宜0.5元，结果比用原价多买了20瓶，求原价每瓶多少元？设原价每瓶x元，则可列出方程为（   ）

1869年，门捷列夫发现了元素周期律，使得化学学习和研究变得有规律可循．下表列出的是1﹣18号元素的部分最高正化合价和最低负化合价．请阅读并回答下列问题：