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.

下列函数中，是二次函数的是（　　）