根据短文理解，从A、B、C三个选项中选择最佳答案填空。

    A young father was visiting an old man. They were standing in the old man's garden and  1  children. The young man said, "How strict should parents be  2their children?" The old man pointed to a line3 a big, strong tree and a thin, 4  one. "Please untie the line," he said. The young man 5 so, and the young tree bent(弯曲) over to one side.

    "Now tie it again," said the old man, "but first pull the line tight(紧紧地) so that the young tree is6  again." The young man did as the old man told him. Then the old man said, "It is the same with  7  . You must be strict with them, but sometimes you must untie the 1ine8 how they are getting on. If they are not yet able to stand alone, you must tie the line tight 9 . But when you find that they are ready to stand alone, you can take the10   away."

对下面材料提取关键词正确的一项是（     ）
        窥探一个成功人的履痕，无一例外，他首先是在于扮演好自己的角色。“一屋不会扫”的人，自然也“扫不了天下”。所以，见到茂密的森林，你只要无愧地做了丛林中最挺拔的一棵；在奔腾的大海面前，你只要无愧地把自己化作浪花里最纯净的一滴水珠；抬头仰望无边无垠的蓝天，你只要毫无愧疚地让自己变为朵朵云中的最祥和的一朵——这样的人生就够了。

根据句子意思，从方框中选择合适的短语填空。