2009年曹操墓的发现，使曹氏及其家人的故事再次成为热议话题，此正是“岁月带不走那一串串熟悉的姓名”。在历史记载和民间话本等诸多材料中，曹操形象犹如川戏之“变脸”。研究发现，曹操在戏台上虽是白脸，实是了不起的人物，几个儿子都才兼文武。曹丕多才多艺，会使剑，在宴席前曾以甘蔗代替，击败对手。反而是号称有八斗之才的曹植，武的方面差。有人则分析指出曹植一直希望能有机会带兵打仗，只是始终未能获得准许而已。还有研究者认为，曹植之所以渴望上前线，并非真想立功建业，只不过是想离开牢狱式的“封邑”。这说明（    ）

科研人员围绕培育四倍体西瓜进行了探究，实验中，每个实验组选取50株西瓜幼苗，并用不同浓度的秋水仙素溶液处理它们的幼芽，得到如图所示的结果．下列分析正确的是（    ）

一项任务，第一天完成 $\frac{1}{3}$ ，第二天完成 $\frac{2}{5}$ ，还剩这项任务的____（填分数）。

根据短文内容及首字母提示，填写所缺单词，使短文意思完整。每空限一词。
Dear Peter,
       I'm glad to receive your letter. Thank you for your caring for the weather and my health. Now I'd like to tell you something a____ the smog（雾霾）.
Since the winter last year, the smog has t____ place for several times. It has done great harm to our d____  life. Many traffic accidents happened just because of the heavy smog weather. More and more people have to go to see the d____  because of the serious disease caused by the smog. Quite a lot of flights have to be put off. A great number of people have to stay at h____ for fear of the poisonous air caused by the smog.
      People have realized the great harm caused by the smog and the importance of p____  the environment. People from all over the country are taking actions to reduce the smog weather. The g____  asks people to go to work or school with the public traffic, such as the bus and the u____ . Also we should plant more trees.
    According to me, I will go to school by bike or on foot, and I won't throw the waste a____ . In addition, I will tell the people that all of us should try our best to protect the environment. Would you like to tell me some good ideas? I'm looking f____  to your reply.
Yours,
Wang Hua

阅读一段文字，再回答下列问题：已知在平面内两点的坐标为P₁（x₁，y₁），P₂（x₂，y₂），则该两点间距离公式为 $P_1{P}_2=\sqrt{{\left(x_2-x_1\right)}^2+{\left(y_2-y_1\right)}^2}$ ．同时，当两点在同一坐标轴上或所在直线平行于x轴、垂直于x轴时，两点间的距离公式可化简成|x2－x1|或|y2－y1|．