阅读下面短文，掌握大意，然后从A、B、C、D四个选项中选出最佳选项。
I once had little passion(激情) in my life. But what happened the other day changed my mind. It was then that I learned how 1 it is to have a passion in life.
That day I went home in Mom's car. When Mom 2 at a red light, someone on the side of the road caught my eye. It was a man dressed 3 old clothes. He was homeless. That didn't interest me, because I had seen 4 like him before. Those people usually looked unhappy and hopeless.
But this man was 5 in some way. He was not sitting down 6 but dancing happily to the music with a 7 in his hand. The radio seemed to be the most important thing for him.
"Mom, why does that man have a radio 8 he's homeless?" I asked.
"He 9 it," she answered.
"10 why doesn't he use the money to buy food or clothes? He paid for something that he didn't need."
"Well, Sarah, sometimes food and clothes aren't the most important."
That man must care more about 11 than food or clothes. I soon realized that 12 is the key to life.
Since then I am always 13 what is truly important in life. A home, a meal, clothes—these things are 14 part of the life. What we often forget is that we all need a joy, a light in a 15 day. We all need a passion which gives a person the happiness to keep going.