Выпишите из текста 2 предложения с модальными глаголами и их эквивалентами. Forests are important components of geographic environment and biosphere. They can be useful in many ways. Forests give us wood and other valuable raw materials and they are a vital part of the biosphere. Forests regulate the water balance, the climate, the chemical composition of the air, the hydrological conditions in rivers, protect against soil erosion. Approximately 50 to 200 liters of water may be stored under one square meter of forest soil. Huge quantities of water are retained by vast mountainous forests where precipitation is high, thus preventing erosion and flood damage. Forest trees filter dust and soot out of the polluted air. The air in the forest therefore contains 200 to 1000 times less pollutants than are found over industrial cities. Trees, moreover, produce oxygen. Twenty mature trees furnish the oxygen needed by one single human being. Spruce trees especially absorb the toxic sulfur dioxide. Their large needle and branch surfaces filter the poison out of the air. This is detrimental if poison concentrations are too high. Trees start declining, growth slows down, and they finally die. Protective forest planting is of great importance on agricultural land. It helps to raise crop yields and prevent soil erosion. Besides, the forest offers opportunity for pleasure and rest for both young and old. The crown canopy prevents extremes of temperature, and therefore on hot summer days and during extremely cold winter nights temperatures are mitigated considerably.