Mrs Black lived in a city of England. Her husband died two years ago and one of her children worked in the capital and the other three lived in another town. Her husband didn't leave her much money and she had to live a simple life. Sometimes her children went to see her during their holidays，but they stayed with her for only two or three days. Luckily she had a cat with her. She liked it very much and took it everywhere she went.    One winter morning the old woman got up early. She was going to buy some food in a shop. And when she came out, she found there was much snow in the street. She had to sweep it away. And suddenly she found the cat at the corner of the house. And then she laughed .Her cat caught a big mouse.

“桃花乱落如红雨”，桃花（如图所示）在发育形成果实的过程中不会凋落的结构是（  ）