在我们的天气日历中可以用简化的风速等级来划分为____、____和____三个等级。

假定英语课上老师要求同桌之间交换修改作文, 请你修改你同桌写的以下作文。文中共有10处语言错误, 每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。

增加：在缺词处加一个漏字符号（∧）, 并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线, 并在该词下面写出修改后的词。

注意：1.每处错误及其修改均限一词；2. 只允许修改10处, 多者（从第11处起）不计分。

Dear Peter,

    I'm writing to tell you something about e-hongbao, that is very popular in China.

    E-hongbao is actual a kind of lucky money from and to relatives and friends during festivals or in special occasions. For many young people, grabbing e-hongbao on our mobile phones is a fairly exciting activity. Unlike the tradition of elders give lucky money to children, over half of the people sending e-hongbao is in their 20s. It's just for fun but giving best wishes, while the sum of money matters a little. In a word, e-hongbao is bringing new color to the old tradition.

    Now I'm concerned about the safe of online payment, and rules and regulations needed to be improved to guarantee its operation.

Best wishes.

Yours,

Li Hua

$△ABC$是边长为2的正三角形，则$\overrightarrow{AB}·\overrightarrow{BC}$ =（     ）

“庞然大物”“黔驴技穷”“黔驴之技”均可比喻本领不过如此，被人看穿，多用于贬义，讽刺人的技能低劣，遭遇无法解决的窘境等等。请同学们试用这几个成语分别造句。