阅读下面短文，掌握其大意，然后从下列各题所给的四个选项（A、B、C、D）中，选出最佳选项。

    A man wanted to become wealthy. He was told a story one day that there was a 1 pebble (鹅卵石）among the pebbles on the beach of the Black Sea. It could turn everything it touched into 2. This pebble could be 3 only by touching it: unlike the other pebbles it was 4 when touched. The man rushed to the beach of the Black Sea and began to 5 the pebble.

    6 he picked up a pebble that felt cold, he threw it into the sea. He 7 this practice day after day. Each pebble that felt cold was 8 thrown into the sea.

    One morning, he 9 to take hold of a pebble that felt warm, unlike the other  10. The man threw the pebble into the sea. He hadn't 11 to, but he had formed a habit. Habits can be hard to 12.

    In fact, if we repeat any behaviour 13 enough, it becomes a habit. But some habits can work in our favour, such as 14 attitudes and healthy ways of life. Our habitual attitudes and behaviour can either 15 us or hinder(阻碍) us.

    Is there behaviour or an attitude you would like to make into a 16? Then reinforce (强化) it by  17 it at every opportunity.

When it comes to habits, 18 may not make perfect. But practice will certainly form 19 behaviour. Your habits will form who you are. So form the habits that are 20to you and let them mold (塑造) you into the person you want to be.