Reading Comprehension

Read the passage and answer the question.

Many cities are now planting trees not only for beauty but to combat a problem called the urban heat island effect. Concrete and asphalt absorb sunlight during the day and release it slowly at night, keeping built-up areas several degrees warmer than the surrounding countryside. Trees help in two ways. Their leaves shade streets and buildings, reducing the amount of heat that surfaces absorb. At the same time, trees release water vapor through their leaves, a process that cools the surrounding air much as sweating cools the human body. Together these effects can noticeably lower temperatures in neighborhoods with abundant greenery.