根据短文内容，选择最佳答案。
One year, a college in the Unites States announced that it would offer a lot of money for the pure white marigold(金盏花). The high reward attracted so many people, but in the nature, besides golden, the marigold is brown, and it is not easy to get the white one. So after they were excited for a time, many people had forgotten the announcement.
One normal day after 20 years, the college received a letter and 100 seeds of pure white marigold. It turned out to be an old woman of over 70 years old. Some experts in the college doubted it, but in order not to let her down, those seeds finally took root(根) in the earth. The miracle appeared after one year: the field was covered by pure white marigold. Therefore, the old woman who was always unknown to the public became a newfocus.
The old woman was a flower-lover. When she read the announcement 20 years ago, she got very excited like others. But her right children were totally against her decision. After all, a woman who never knew the seed genetics(遗传学) couldn't complete what the experts could never do, so her thought was only a day dream.
Still, the old woman didn't change her mind and went on working. She planted some of the most common seeds and took good care of them. A year later, when the marigold came out, she chose one faintest(最暗淡的) from those golden and brown flowers and get the best seed. The next year, she again grew them and chose…… Day after day, year after year, through many seasons, the old woman's husband died, her children flew far and high, a lot of things happened in her life, but only the desire to grow the pure white marigold took root in her heart.
Finally, after 20 years on the day we all know, in the garden she saw a marigold which was not nearly white, but as white as sliver or snow.
A problem even experts couldn't deal with was solved by an old woman who didn't understand genetics. Wasn't it a miracle?
To take root in the heart 
even the most common seed can grow into a miracle!
