根据牛顿第二定律，下列叙述正确的是（   ）

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.