阅读下列短文，从文后各题所给的四个选项中选出一个最佳答案。

    There was once a millionaire who loved money more than anything else in the world. He didn't know exactly（精确地） how much he had, so he took on a little girl to  1 all his money for him.

    It 2 the little girl six days to count all the money. When she told the millionaire that he had forty-two3dollars, he was 4  with joy and asked, “How much 5 do you want?” He thought that 6 she was only a child, he could 7 her into taking a very small amount of money.

    The girl said, “Well, I worked for six days, so I think you 8 pay me for six days. Give me two pennies（便士） for the first day. Each day after that, just give me the amount you give me the day before, multiplied by（乘以） itself.”

    The9 thought that in this 10 he would only have to give her a 11dollars. What a12 little girl! So immediately, he 13his lawyer sign up the contract（契约）, fearing（害怕） that she would change her 14.

    On the first day the millionaire paid her two pennies, and on the second day, two pennies times two pennies, or four pennies.

    Each day after that, he gave her 15 number of pennies he had given her the day before, multiplied by itself. And by the sixth day, the foolish millionaire had to give the clever little girl all his money.