—Would you mind picking up the last cigarette on the playground?

—_______. I'll do it right away.

2012年3月1日起，厦门是全国第二个每日发布PM2.5监测数据的城市。PM2.5是大气中可吸入肺颗粒物，直径不到人头发丝粗细的1/20，它的直径小于或等于2.5（      ）

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仅限一词；2.只允许修改10处，多者（从第11处起）不计分。

Dear editor,

    I am Evan from Canada. Being the oldest child in the family has its disadvantages. First of all, I have to share all my toys with my young sisters. Of course, they don't need to return to the favor because I'm total uninterested in their things. Besides, they are always hanging around me. I just can't get moment's peace. At meals, I have to eat whichever is on the plate regardless of the taste. My sisters only try one bite if it's not our favorite food. In addition, when it comes to practice our musical instruments, I have to practice more than double the time. Worst of all, I got a larger quantity of housework. Comparing to them, I'm feeling rather annoyed. Can you please give me some advices?

Yours truly,

Evan Smith

在直角坐标系 $xOy$ 中，直线 $l_1$ 的参数方程为 $\{\begin{array}{c}x=t-\sqrt{3}\\ y=kt\end{array}$ （ $t$ 为参数），直线 $l_2$ 的参数方程为 $\{\begin{array}{c}x=\sqrt{3}-m\\ y=\frac{m}{3k}\end{array}$ （ $m$ 为参数），设 $l_1$ 与 $l_2$ 的交点为 $P$ ，当 $k$ 变化时， $P$ 的轨迹为曲线 $C_1$ .