关于声现象，下列说法中正确的是（　　）

    All kinds of people come in to have their shoes shined. Most folks are friendly. But this man was different.

    “How much do you make a week, boy？” he asked me. I felt he was 1 at me. He kept giving a sharp 2 around every now and then. All the time I kept 3 where I'd seen his face. Suddenly I knew. I'd seen his4in the post office many times. He was the big robber 5 by the police in three states!

    “You know，” he was saying, “it's imagination that people lack. You'll never get anywhere as a 6 boy.”

    I kept brushing away on his shoes as 7 as I could. The sooner I finished, the better. He said, “When I was sixteen, I had8 $2,500 of my own.”

    That reminded me of something. Was it $2,500 or $5,000 or $7, 500? I wasn't 9. I knew a big reward was 10 for him.

    But what could I do about it?11him with a can of shoe polish? A man of his 12 could grind (碾碎) me into the floor. If only someone would come in!

    He kept talking away. “Along with13， it takes courage. The courage to take a chance. Start something on a shoestring.”

    Suddenly I saw Officer Dailey 14 across the street. Then, real fast, I began tightening the man's shoestrings.

    The policeman was at the window when I cried out, “Officer Dailey,15！ This man's a robber.”

    “16，” the man shouted angrily. He started to jump off the stand. But he didn't go the way he 17. He fell flat on his face and knocked himself out cold.

    “That was pretty 18 of you，” the officer said. “You'll get a reward of $7,500 for him.”

    “Well, it really wasn't my 19，” I said. “It was his. He told me if you had courage and imagination you could start something big on a 20.”

Look! The people ____ (swim) in the lake now.