Câu hỏi:

Read the passage and choose the best answer to each of the following questions

Trees contribute to their environment by providing oxygen, improving air quality, conserving water, preserving soil, and supporting wildlife. During the process of photosynthesis, trees take in carbon dioxide and produce the oxygen we breathe. Trees, shrubs and turf also filter air by removing dust and absorbing other pollutants like carbon monoxide, sulfur dioxide and nitrogen dioxide. After trees intercept unhealthy particles, rain washes them to the ground.Trees control climate by moderating the effects of the sun, rain and wind. Leaves absorb and filter the sun’s radiant energy, keeping things cool in summer. Trees also preserve warmth by providing a screen from harsh wind. In addition to influencing wind speed and direction, they shield US from the downfall of rain, sleet and hail. Trees also tower the air temperature and reduce the heat intensity of the greenhouse effect by maintaining tow levels of carbon dioxide.Both above and below ground, trees are essential to the eco-systems in which they reside. Far reaching roots hold soil in place and fight erosion. Trees absorb and store rainwater, which reduces runoff and sediment deposit after storms. This helps the ground water supply recharge, prevents the transport of chemicals into streams and prevents flooding. Fallen leaves make excellent compost that enriches soil.Many animals, including elephants, koalas and giraffes eat leaves for nourishment. Fruits are eaten by monkeys, and nectar is a favorite of birds, bats and many insects. Animals also eat much of the same fruits that we enjoy. This process helps disperse seeds over great distances. Of course, hundreds of living creatures call trees their home. Leaf-covered branches keep many animals, such as birds and squirrels, out of the reach of predators.(From Importance and Value of Trees - savatree.com)

Which is the passage mainly about?