阅读下面短文，从短文后所给的A、B、C、D四个选项中选出能填入相应空白处的最佳选项。

    Mr. Black was over fifty years old. He sometimes made some mistakes in his work, and he lost his work. So he had 1 time every day to do something. Then he often met his old friends under a big tree. They had drinks there and talked 2 anything they liked.

    One day, some old men were sitting together again and talking about young people in this world. They all agreed that the old people were 3 than young people. Then one of the old 4 said that young men were stronger than old men. 5 of them agreed that this was true, 6 Mr. Black didn't. He said, “No. I am as strong now as when I was a young man.” His friends were surprised 7 what he said. “Well,” said Mr. Black, “Near my house there is a big stone. When I was a young man, I used 8 to move it, but I couldn't because I was not 9. I am an old man now, and when I try to move it, I still 10. So, I am as strong as when I was young.”