阅读短文，回答问题
Last Summer Maria and her mom moved from the countryside to a tall building in the city. Maria really liked many things about the city, but she missed her house and yard (院子) in the countryside.
One day Maria was in her room when she saw her neighbor, Mrs. Garcia, carrying a gardening tool (园林工具) and a bag of soil. Maria wanted to know how Mrs. Garcia could garden in the city. She went out and met her.
"My mom can grow the most delicious vegetables, and I know she misses her garden, but we don't have a yard," said Maria.
Mrs. Garcia laughed and said, "I'll show you," she said.
Maria thought Mrs. Garcia would take her to a park or somewhere else, but she took her to the roof (房顶). When the door opened, Maria was surprised to see so many flowers and vegetables on the roof.
"What an excellent garden!" said Maria.
Mrs. Garcia told Maria that for a long time the roof was an empty (空的) place. Then some of the people in the building asked the owners to turnitinto a garden. The building owners liked the idea because the plants not only (不但) helped to keep the air clean, but also (而且) they helped to keep the buildings cool in hot weather.
"I plant flowers in my garden," Mrs. Garcia said, "but you will be surprised how different the plants are up here. Some people grow vegetables just like your mom. You can do some of the same things in the city as in the countryside."
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