阅读下列短文, 从题中所给的四个选项（A、B、C和D）中选出最佳选项。
A
There used to be many beautiful flowers in our garden. Among them was a beautiful blue flower. My husband once told me that it only bloomed (开花) in spring and the sun in summer was too hot for it. When summer came, he would move it out of the garden and put it inside our house.
Once, my husband was away for some time on business, so I had to take care of the flowers. Before leaving, he told me to pay special attention to the blue flower. I planned to look after it as my husband had ever done, but I was too busy to remember it. One weekend when I wanted to move the blue flower into the house, I found that it had already died. I was very sad and regretted not taking good care of it earlier.
A week ago, my husband's elder sister, Linda, died of serious stomach cancer. Linda was much older than my husband. Maybe because of the age distance, we were not very close. After she died, we were very sad and regretted not visiting her often.
Linda's death reminds me of the blue flower. We should have done something better, but we haven't tried our best. I believe that God has given us enough time to plant some wonderful things that will bloom inside us, but we have missed it.
r=
d=
是正方形d=
长方形的周长是