植物是我们生活中必不可少的一个部分，那么你知道植物的重要性吗？
Plants form the basic food staple for all life forms.They are the major source of food and oxygen on earth，since no animal can supply these necessary components without plants.
There are many different types of cash crops that produce money for farmers.Olive oil comes from olives，corn oil comes from corn，and peanut oil comes from peanuts.Typical agricultural products like corn，wheat，rye，and rice are all considered cash crops.Coffee plants produce beans that are used to make coffee；coca plants give us chocolate；vanilla plants grow long thin beans that are used to produce vanilla flavoring.
Plants are also used in agriculture to help reduce wind speed.Planting trees in a row prevents the wind from blowing away the valuable topsoil.In the forest，trees act as shelter for many organisms.
Plants are also important for the overall ecology of an area.Roots help to stabilize soil and prevent the soil erosion by water runoff.
Plants are also important in our atmosphere because they use carbon dioxide and give off oxygen while they undergo photosynthesis.
Plants are also used in the urban setting to reduce noise，produce shade，and to beautify an area.Trees add value to homes and communities.
Plants are essential to the balance of nature and in people's lives.Green plants，i.e.，those possessing chlorophyll(叶绿素)，produce their own food and give off oxygen in the process called photosynthesis (光合作用)，in which water and carbon dioxide are combined by the energy of light.Plants are the ultimate source of food and metabolic energy for nearly all animals，which cannot produce their own food.Besides foods，plant products vital to humans include wood and wood products，fibers，drugs，oils，latex，pigments，and resins.Coal and petroleum (石油) are fossil substances of plant origin.Thus plants provide people not only sustenance but shelter，clothing，medicines，fuels，and the raw materials from which innumerable other products are made.
两个诱思问题
1．What is the purpose of the second paragraph?
2．Why are plants important to our atmosphere?
【答案】 1.Give some examples about the use of plants.
2.Because they use carbon dioxide and give off oxygen while they undergo photosynthesis.
