读下图，回答以下题目。

下图为城市建设前后水循环示意图。读图回答下列各题。

用一个平面去截一个正方体，截面可能是（　　）

短文改错。便条中共有10处错误,每句中最多有两处。错误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（∧）。并在其下面写出修改后的词。
删除：把多余的词用斜线（＼）划掉。
修改：在错的词后划一横线,并在该词下面写出修改后的词。
注意：1）．每处错误及修改均仅限一词;
2）．只允许修改10处,多者（从第11处起）不记分。
    One day, I was cooking in the kitchen when the telephone rings. I went to answer it immediately. She was my close friend, Lisa. When we were talking on a phone, the fire alarm sounded. I dashed back to the kitchen. The room full of smoke and the beef was bad burnt. I quickly turned off the gas, opening all the windows, and then rushed out of the house. In my surprise, two fire engines were outside my house. I was rather worrying. I told about the firemen that it was my careless cooking which caused the heavy smoke.

某同学要测量凸透镜的焦距，他把凸透镜正对着太阳光，把一张白纸放在凸透镜的另一侧，改变凸透镜与纸之间的距离，直到纸上的光斑变得最小、最亮，如图所示．此时光斑与凸透镜光心之间的距离就是该凸透镜的焦距．