سؤال ۱۳، زبان انگلیسی ۳، دی ۱۳۹۸

a. They also cause rain.b. The rain makes the air fresh and clean.c. Trees are very valuable.d. Thus, trees play a big and important role in our life.e. They supply us with many necessary things of everyday life.f. For example, they take carbon dioxide from the atmosphere and fill it with oxygen.