先通读下面的短文，掌握其大意，然后在每小题所给的A、B、C、D四个选项中，选出可以填入空白处的最佳选项。

    About ten years ago, both of my parents lost their jobs. Life was1 for me then. I 2at the gift shop in my university's museum in my spare time. One day 3 working in the shop, I saw an elderly couple come in with a little girl in a wheelchair.

    As I looked closer at this girl, I found that she had no arms or legs, just a head, neck and body. She was wearing a pretty white dress and a little red4. When they came closer to me, I 5 her a wink(眨眼). And the girl gave me the most beautiful 6that I had ever seen.

    All of a sudden, her handicap(残疾) was gone and all that I saw was a 7girl. I was deeply moved by her smile, and I8what life was all about. She brought me, a poor and unhappy college student, into her world full of smiles, 9and warmth.

    I'm a successful business person now. Whenever I am in low spirits and in10I always think of that little girl and the lesson about life that she taught me.

【多彩中华，世界大同】

    G20杭州峰会文艺演出“最忆是杭州”给我们带来了一场震撼的视觉盛宴。这是一台彰显中西合璧、文化交融的演出：以天为幕、以桥为景、以湖为台，各方来宾置身于湖光山色中，聆听经典名曲，观看水上歌舞，感受中国神韵与世界文化的交融与对话。文化艺术是不同国家和民族相互了解和沟通的最好方式，无论是色彩、音符，还是线条、舞步，都能跨越时空的障碍，消除语言的藩篱，直指人心，互通情意，使各民族文化元素水乳交融。

阅读完材料后，请回答：

如图，在平面直角坐标系xOy中，若动点P在抛物线y=ax²上，⊙P恒过点F（0，n），且与直线y=﹣n始终保持相切，则n=____（用含a的代数式表示）．