阅读下列材料，回答问题：

2017年春节刚过，一股弥漫着禽流感的信息扑面而来，据权威机构发布：1月份全国感染H7N9的人数达到192人，79人死亡．5月19日，滨州医学院附属医院也确认一例H7N9禽流感病例．H7N9禽流感是通过接触禽类而导致人感染，因此，禽流感成为蛋鸡养殖业的克星，养鸡市场迎来一片哀嚎．对于预防H7N9禽流感专家提出以下建议：①对患者进行隔离治疗；②勤洗手，注意个人卫生；③避免去人群密集、空气污浊的场所，特别避免去有活禽交易的市场；④经常锻炼身体，提高自身身体素质等．

体积相等的实心铜球和实心木球在水平地面上以相同的速度做匀速直线运动，铜球的动能为E_K铜，木球的动能为E_K木。已知铜的密度大于木头的密度，则（　　）

如图甲所示，Q₁、Q₂为两个被固定的点电荷，a、b是它们连线的延长线上的两点．现有一带负电的粒子只在电场力作用下以一定的初速度从a点开始经b点向远处运动，粒子经过a、b两点时的速度分别为v_a、v_b，其速度时间图象如图乙所示．下列说法正确的是（   ）

    For some time, I had been thinking that I wanted to do something to make strangers smile. I decided that I ____ (leave) small notes around shops and other public places with positive sayings or kind words for strangers ____ (find).

    A friend on Facebook posted that she had received a lot of beautiful paper from an artist friend and was wondering what to do with it. I told her about my idea, and she ____ (immediate) said that this must be what her paper was meant for.

    So two friends on opposite ____ (side) of the world started leaving these random notes of kindness. I leave my notes without ____ (expect) any particular result. It doesn't matter whether they are read ____ thrown away. The main thing is that I did this act.

    I now carry around a notebook in ____ I write down lovely and inspiring phrases that I find. And I buy packs of Post­ its to write notes on whenever I see ____ opportunity to make a stranger smile. I only leave the notes when I am feeling in a ____ (happily) mood, as I don't want to pass any negative energy on to someone else.

    I sign them all ____ (say) that this note is left for you by a stranger to make you smile. Then, I add a heart.